Biomedical subjects

Hyun-Sook Pai

Publications and source records attributed to Hyun-Sook Pai.

At least 19 recordsLinked to original sources

PubMed2007

Silencing of NbBTF3 results in developmental defects and disturbed gene expression in chloroplasts and mitochondria of higher plants.

BTF3 (betaNAC) was originally isolated as a general transcription factor required for RNA polymerase II-dependent transcription, and later found to be a beta-subunit of nascent-polypeptide-associated complex that has been implicated in regulating protein localization during translation. In this study, virus-induced gene silencing of NbBTF3 encoding a Nicotiana benthamiana homolog of human BTF3 caused leaf yellowing and abnormal leaf morphology without altering the overall growth of the plant. The NbBTF3 gene is constitutively expressed and the NbBTF3-GFP fusion protein is primarily targeted to the nucleus. At the cellular level, downregulation of NbBTF3 expression reduced the chloroplast sizes and chlorophyll contents. The affected cells produced excessive amounts of reactive oxygen species. Furthermore, the transcript level of various plastid- and mitochondria-encoded genes was severely reduced in the NbBTF3-depleted leaf cells. These findings indicate that depletion of NbBTF3 activity preferentially affected development and/or physiology of chloroplasts and mitochondria in plants, possibly by hampering efficient translocation of the nascent organellar proteins into the organelles.

Amino Acid Sequence↗

PubMed2007

A split enhanced green fluorescent protein-based reporter in yeast two-hybrid system.

We have developed a novel reporter system involving a yeast two-hybrid assay, which utilizes the reconstitution of the split EGFP reporter in order to characterize the relevant protein-protein interactions. To our knowledge, this study represents the first application of the split EGFP system as a read-out in a yeast two-hybrid assay. In comparison with the existing two-hybrid system, the bait and prey vectors were improved with regard to the reporter and the replication control element. As a result, the reconstituted EGFP has been observed to evidence a restored fluorescence upon protein-protein interactions in yeast, thereby allowing for the characterization of its interactor. The use of a split EGFP reporter has some salient advantages. Firstly, no substrates are required for the production of fluorescence. Secondly, low copy number plasmids may help to solve the protein toxicity problem, via the reduction of expression. Thirdly, this technique may prove useful in overcoming the autoactivation problem, due to the fact that the read-out of the yeast two-hybrid system is transcription-independent. Collectively, our results showed that the split EGFP reporter system might potentially be applied in yeast two-hybrid assays for the high-throughput screening of protein-protein interactions, with a simple and direct fluorescent read-out.

Escherichia coli↗

PubMed2006

Mitochondria-associated hexokinases play a role in the control of programmed cell death in Nicotiana benthamiana.

Recent findings suggest a pivotal role for mitochondria-associated hexokinase in the regulation of apoptosis in animal cells. In this study, virus-induced gene silencing (VIGS) of a hexokinase-encoding Hxk1 caused necrotic lesions on leaves, abnormal leaf morphology, and retarded plant growth in Nicotiana benthamiana. Hxk1 was associated with the mitochondria, and this association required the N-terminal membrane anchor. VIGS of Hxk1 reduced the cellular glucose-phosphorylating activity to approximately 31% of control levels without changing the fructose-phosphorylating activity and did not alter hexose phosphate content severely. The affected cells showed programmed cell death (PCD) morphological markers, including nuclear condensation and DNA fragmentation. Similar to animal cell apoptosis, cytochrome c was released into the cytosol and caspase-9- and caspase-3-like proteolytic activities were strongly induced. Furthermore, based on flow cytometry, Arabidopsis thaliana plants overexpressing Arabidopsis HXK1 and HXK2, both of which are predominantly associated with mitochondria, exhibited enhanced resistance to H(2)O(2)- and alpha-picolinic acid-induced PCD. Finally, the addition of recombinant Hxk1 to mitochondria-enriched fractions prevented H(2)O(2)/clotrimazole-induced cytochrome c release and loss of mitochondrial membrane potential. Together, these results show that hexokinase critically regulates the execution of PCD in plant cells, suggesting a link between glucose metabolism and apoptosis.

Apoptosis↗

PubMed2006

Depletion of UDP-D-apiose/UDP-D-xylose synthases results in rhamnogalacturonan-II deficiency, cell wall thickening, and cell death in higher plants.

D-apiose serves as the binding site for borate cross-linking of rhamnogalacturonan II (RG-II) in the plant cell wall, and biosynthesis of D-apiose involves UDP-D-apiose/UDP-D-xylose synthase catalyzing the conversion of UDP-D-glucuronate to a mixture of UDP-D-apiose and UDP-D-xylose. In this study we have analyzed the cellular effects of depletion of UDP-D-apiose/UDP-D-xylose synthases in plants by using virus-induced gene silencing (VIGS) of NbAXS1 in Nicotiana benthamiana. The recombinant NbAXS1 protein exhibited UDP-D-apiose/UDP-D-xylose synthase activity in vitro. The NbAXS1 gene was expressed in all major plant organs, and an NbAXS1-green fluorescent protein fusion protein was mostly localized in the cytosol. VIGS of NbAXS1 resulted in growth arrest and leaf yellowing. Microscopic studies of the leaf cells of the NbAXS1 VIGS lines revealed cell death symptoms including cell lysis and disintegration of cellular organelles and compartments. The cell death was accompanied by excessive formation of reactive oxygen species and by induction of various protease genes. Furthermore, abnormal wall structure of the affected cells was evident including excessive cell wall thickening and wall gaps. The mutant cell walls contained significantly reduced levels of D-apiose as well as 2-O-methyl-L-fucose and 2-O-methyl-D-xylose, which serve as markers for the RG-II side chains B and A, respectively. These results suggest that VIGS of NbAXS1 caused a severe deficiency in the major side chains of RG-II and that the growth defect and cell death was likely caused by structural alterations in RG-II due to a D-apiose deficiency.

Carbon-Nitrogen Ligases↗

PubMed2006

Functional characterization of NtCDPK1 in tobacco.

We previously showed that NtCDPK1, a tobacco cal-cium-dependent protein kinase, interacts with and phosphorylates the Rpn3 regulatory subunit of the 26S proteasome, and that both NtCDPK1 and Rpn3 are mainly expressed in rapidly proliferating tissues, in-cluding shoot and root meristem. In this study, we ex-amined NtCDPK1 expression in roots using GUS ex-pression in transgenic Arabidopsis plants, and investi-gated its function in root development by generating transgenic tobacco plants carrying a sense NtCDPK1 transgene. GUS activity was first detected in roots two days after sowing. In later stages, strong GUS expres-sion was detected in the root meristem and elongation zone, as well as the initiation sites and branch points of lateral roots. Transgenic tobacco plants in which NtCDPK1 expression was suppressed were smaller, and their root development was abnormal, with reduced lateral root formation and less elongation. These re-sults suggest that NtCDPK1 plays a role in a signaling pathway regulating root development in tobacco.

Arabidopsis↗

PubMed2006

Comparative microarray analysis of programmed cell death induced by proteasome malfunction and hypersensitive response in plants.

Programmed cell death (PCD) plays a pivotal role in the elimination of injured or unwanted cells during diverse physiological and developmental conditions in organisms. However in contrast to the animal system, signaling pathways and molecular mechanism of PCD are largely unknown in plants. We previously reported that silencing of NbPAF encoding the alpha6 subunit of 20S proteasome by virus-induced gene silencing activated programmed cell death in plants by inactivating proteasome function. In this study, we analyzed global gene expression profile of PCD induced by suppression of NbPAF expression, in comparison with that of hypersensitive response (HR)-induced PCD, using a cDNA microarray representing 4685 hot pepper genes. HR is a well-characterized PCD program in plants, which occurs in response to pathogen infection. The microarray analyses identified 247 genes whose gene expression was differentially modulated during PCD activated by NbPAF depletion or HR. Most of the genes that were up-regulated during the NbPAF-mediated PCD, including the ubiquitin/proteasome pathway-related genes, were down-regulated during HR cell death. In contrast, transcription of many defense-related genes, transcription factor genes, and photosynthesis-related genes remained unchanged or repressed during NbPAF-mediated PCD, while it was highly induced during HR cell death. Only a small number of genes including antioxidant-related genes and proteases were found to be up-regulated during induction of PCD by both proteasome inactivation and HR. Based on these results, these two PCD pathways appear to be differentially regulated, but some overlapping mechanism exists, which involves core regulators of plant PCD.

Apoptosis↗

PubMed2006

Prohibitin is involved in mitochondrial biogenesis in plants.

Prohibitin, which consists of two subunits PHB1 and PHB2, plays a role in cell-cycle progression, senescence, apoptosis, and maintenance of mitochondrial function in mammals and yeast. In this study, we examined the role of prohibitins in plants by using virus-induced gene silencing (VIGS) of two prohibitin subunit genes of Nicotiana benthamiana, designated NbPHB1 and NbPHB2. NbPHB1 and NbPHB2 were targeted to the mitochondria, and their gene expression was suppressed during senescence. VIGS of NbPHB2 caused severe growth inhibition, leaf yellowing and symptoms of cell death, whereas VIGS of NbPHB1 resulted in a milder phenotype. At the cellular level, depletion of these subunits affected mitochondria by severely reducing their number and/or mass, and by causing morphological and physiological abnormalities. Suppression of prohibitin function resulted in a 10- to 20-fold higher production of reactive oxygen species and induced premature leaf senescence. Finally, disruption of prohibitin function rendered the plants more susceptible to various oxidative stress-inducing reagents, including H(2)O(2), paraquat, antimycin A and salicylic acid. These results suggest that prohibitins play a crucial role in mitochondrial biogenesis and protection against stress and senescence in plant cells.

DNA, Complementary↗

PubMed2005

Silencing of NbNAP1 encoding a plastidic SufB-like protein affects chloroplast development in Nicotiana benthamiana.

It was previously shown that AtNAP1 is a plastidic SufB protein involved in Fe-S cluster assembly in Arabidopsis. In this study, we investigated the effects of depleting SufB protein from plant cells using virus-induced gene silencing (VIGS). VIGS of NbNAP1 encoding a Nicotiana benthamiana homolog of AtNAP1 resulted in a leaf yellowing phenotype. NbNAP1 was expressed ubiquitously in plant tissues with the highest level in roots. A GFP fusion protein of the N-terminal region (M1-V103) of NbNAP1 was targeted to chloroplasts. Depletion of NbNAP1 resulted in reduced numbers of chloroplasts of reduced size. Mitochondria also seemed to be affected. Despite the reduced number and size of the chloroplasts in the NbNAP1 VIGS lines, the expression of many nuclear genes encoding chloroplast-targeted proteins and chlorophyll biosynthesis genes remained unchanged.

Adenosine Triphosphatases↗

PubMed2005

Inactivation of organellar glutamyl- and seryl-tRNA synthetases leads to developmental arrest of chloroplasts and mitochondria in higher plants.

Aminoacyl-tRNA synthetases (ARSs) are key enzymes involved in protein translation, and both cytosolic and organellar forms are present in the genomes of eukaryotes. In this study, we investigated cellular effects of depletion of organellar forms of ARS using virus-induced gene silencing (VIGS) in Nicotiana benthamiana. VIGS of NbERS and NbSRS, which encode organellar GluRS and SerRS, respectively, resulted in a severe leaf-yellowing phenotype. The NbERS and NbSRS genes were ubiquitously expressed in plant tissues, and induced in response to light. Green fluorescent protein (GFP) fusion proteins of the full-length glutamyl-tRNA synthetase (ERS) and seryl-tRNA synthetase (SRS) of Arabidopsis and GFP fusions to the N-terminal extension of these proteins were all dualtargeted to chloroplasts and mitochondria. At the cell level, depletion of NbERS and NbSRS resulted in dramatically reduced numbers of chloroplasts with reduced sizes and chlorophyll content. The numbers and/or physiology of mitochondria were also severely affected. The abnormal chloroplasts lacked most of the thylakoid membranes and appeared to be degenerating, whereas some of them showed doublet morphology, indicating defective chloroplast division. Pulse-field gel electrophoresis analyses demonstrated that chloroplast DNA in subgenomic sizes is the predominant form in the abnormal chloroplasts. Interestingly, despite severe abnormalities in chloroplasts and mitochondria, expression of many nuclear genes encoding chloroplastor mitochondria-targeted proteins, and chlorophyll biosynthesis genes remained unchanged in the ERS and SRS VIGS lines. This is the first report to analyze the effect of ARS disruption on organelle development in plants.

Arabidopsis↗

PubMed2005

Silencing of NbECR encoding a putative enoyl-CoA reductase results in disorganized membrane structures and epidermal cell ablation in Nicotiana benthamiana.

The very long chain fatty acids (VLCFAs) are synthesized by the microsomal fatty acid elongation system in plants. We investigated cellular function of NbECR putatively encoding enoyl-CoA reductase that catalyzes the last step of VLCFA elongation in Nicotiana benthamiana. Virus-induced gene silencing of NbECR produced necrotic lesions with typical cell death symptoms in leaves. In the affected tissues, ablation of the epidermal cell layer preceded disintegration of the whole leaf cell layers, and disorganized cellular membrane structure was evident. The amount of VLCFAs was reduced in the NbECR VIGS lines, suggesting NbECR function in elongation of VLCFAs. The results demonstrate that NbECR encodes a putative enoyl-CoA reductase and that the NbECR activity is essential for membrane biogenesis in N. benthamiana.

Amino Acid Sequence↗

PubMed2005

Functional characterization of NtCEF1, an AP2/EREBP-type transcriptional activator highly expressed in tobacco callus.

Using PCR-select cDNA subtraction, we identified the genes that are predominantly expressed in the shooty callus induced by suppression of the CHRK1 receptor-like kinase gene. One of the identified genes encoded a novel AP2/EREBP-type transcription factor, and it was highly expressed in various types of tobacco callus including the CHRK1 transgenic callus, hence designated as Nicotiana tabacum Callus-Expressing Factor 1 NtCEF1. The NtCEF1-GFP fusion protein was localized in the nucleus. The full length and the C-terminal acidic region of NtCEF1 could function as a transactivator in yeast, when fused to the LexA DNA binding domain. Expression of the NtCEF1 gene was induced by ethylene and by various abiotic stresses. Gel retardation assay revealed that NtCEF1 could bind specifically to the GCC box as well as to the C/DRE motif, albeit less strongly. Interestingly, NtCEF1 overexpression in Arabidopsis resulted in constitutive expression of various ethylene-responsive and defense genes that contain the GCC box in the promoter-but none of the genes containing the upstream C/DRE elements-indicating that NtCEF1 preferentially recognizes the GCC box in vivo. Furthermore, the NtCEF1-overexpressing Arabidopsis plants exhibited enhanced resistance to a bacterial pathogen, Pseudomonas syringae pv. tomato DC3000. Taken together, these results suggest that NtCEF1 is a transcription factor preferentially activating the GCC box-containing defense genes, and that it modulates increased resistance against the biotic stress by activation of the downstream gene expression.

Amino Acid Sequence↗

PubMed2005

Retinoblastoma protein regulates cell proliferation, differentiation, and endoreduplication in plants.

Retinoblastoma protein (Rb) plays a key role in cell cycle control, cell differentiation, and apoptosis in animals. In this study, we used virus-induced gene silencing (VIGS) to investigate the cellular functions of Rb in higher plants. VIGS of NbRBR1, which encodes the Nicotiana benthamiana Rb homolog, resulted in growth retardation and abnormal organ development. At the cellular level, Rb suppression caused prolonged cell proliferation in tissues that are normally differentiated, which indicates that Rb is a negative regulator of plant cell division. Furthermore, differentiation of the epidermal pavement cells and trichomes was partially retarded, and stomatal clusters formed in the epidermis, likely due to uncontrolled cell division of stomata precursor cells. Rb suppression also caused extra DNA replication in endoreduplicating leaf cells, suggesting a role of Rb in the endocycle. These Rb phenotypes were accompanied by stimulated transcription of E2F and E2F-regulated S-phase genes. Thus, disruption of Rb function in plants leads to ectopic cell division in major organs that correlates with a delay in cell differentiation as well as increased endoreduplication, which indicates that Rb coordinates these processes in plant organ development.

Cell Differentiation↗

PubMed2004

DNA gyrase is involved in chloroplast nucleoid partitioning.

DNA gyrase, which catalyzes topological transformation of DNA, plays an essential role in replication and transcription in prokaryotes. Virus-induced gene silencing of NbGyrA or NbGyrB, which putatively encode DNA gyrase subunits A and B, respectively, resulted in leaf yellowing phenotypes in Nicotiana benthamiana. NbGyrA and NbGyrB complemented the gyrA and gyrB temperature-sensitive mutations of Escherichia coli, respectively, which indicates that the plant and bacterial subunits are functionally similar. NbGyrA and NbGyrB were targeted to both chloroplasts and mitochondria, and depletion of these subunits affected both organelles by reducing chloroplast numbers and inducing morphological and physiological abnormalities in both organelles. Flow cytometry analysis revealed that the average DNA content in the affected chloroplasts and mitochondria was significantly higher than in the control organelles. Furthermore, 4',6-diamidino-2-phenylindole staining revealed that the abnormal chloroplasts contained one or a few large nucleoids instead of multiple small nucleoids dispersed throughout the stroma. Pulse-field gel electrophoresis analyses of chloroplasts demonstrated that the sizes and/or structure of the DNA molecules in the abnormal chloroplast nucleoids are highly aberrant. Based on these results, we propose that DNA gyrase plays a critical role in chloroplast nucleoid partitioning by regulating DNA topology.

Base Sequence↗

PubMed2004

The CaPRP1 gene encoding a putative proline-rich glycoprotein is highly expressed in rapidly elongating early roots and leaves in hot pepper (Capsicum annuum L. cv. Pukang).

Most of the proline-rich cell wall glycoprotein genes isolated from higher plants are preferentially expressed in the transmitting tissues of the flower organ. In conducting expressed sequence tag (EST) analysis, which was prepared from 5-day-old early roots of hot pepper (Capsicum annuum L. cv. Pukang), we identified a cDNA clone, pCaPRP1, encoding a putative cell wall proline-rich glycoprotein. CaPRP1 (Mr=28 kDa, pI=9.98) was most closely related to Nicotiana alata NaPRP4 (71%), while most distantly related to soybean PvPRP (37%). The predicted primary structure of CaPRP1 contains a putative N-terminal signal peptide, six repeats of the Lys-Pro-Pro tripeptide, four repeats of a five-amino acid sequence [Pro-(Ser/The)-Pro-Pro-Pro] and one potential N-glycosylation site (Asn-Asn-Ser). In contrast to most proline-rich cell wall glycoprotein genes, CaPRP1 was highly expressed in rapidly elongating very early roots and young leaves as well as developing flower tissues. Although the physiological function of CaPRP1 is not yet clear, there are several possibilities for its role in cell expansion and elongation during early development of hot pepper plants.

Amino Acid Sequence↗

PubMed2004

Hypoxia inhibits tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis by blocking Bax translocation.

The hypoxic environment in solid tumors results from oxygen consumption by rapid proliferation of tumor cells. Hypoxia has been shown to facilitate the survival of tumor cells and to be a cause of malignant transformation. Hypoxia also is well known to attenuate the therapeutic activity of various therapies in cancer management. These observations indicate that hypoxia plays a critical role in tumor biology. However, little is known about the effects of hypoxia on apoptosis, especially on apoptosis induced by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a potent apoptosis inducer that has been shown to specifically limit tumor growth without damaging normal cells and tissues in vivo. To address the effects of hypoxia on TRAIL-induced apoptosis, HCT116 human colon carcinoma cells were exposed to hypoxic or normoxic conditions and treated with soluble TRAIL protein. Hypoxia dramatically inhibited TRAIL-induced apoptosis in HCT116 cells, which are highly susceptible to TRAIL in normoxia. Hypoxia increased antiapoptotic Bcl-2 family member proteins and inhibitors of apoptosis proteins. Interestingly, these hypoxia-increased antiapoptotic molecules were decreased by TRAIL treatment to the levels lower than those of the untreated conditions, suggesting that hypoxia inhibits TRAIL-induced apoptosis via other mechanisms rather than up-regulation of these antiapoptotic molecules. Additional characterization revealed that hypoxia significantly inhibits TRAIL-induced translocation of Bax from the cytosol to the mitochondria in HCT116 and A549 cells, with the concomitant inhibition of cytochrome c release from the mitochondria. Bax-deficient HCT116 cells were completely resistant to TRAIL regardless of oxygen content, demonstrating a pivotal role of Bax in TRAIL-induced apoptotic signaling. Thus, our data indicate that hypoxia inhibits TRAIL-induced apoptosis by blocking Bax translocation to the mitochondria, thereby converting cells to a Bax-deficient state.

Antineoplastic Agents↗

PubMed2004

Molecular characterization of NbCHMP1 encoding a homolog of human CHMP1 in Nicotiana benthamiana.

In humans, CHMP1 encodes a protein of dual function that plays a role in both modification of chromatin structure and endosomal vesicle trafficking. Recently, it was found that sal1, a CHMP1 homolog in maize, is important for the development of the aleurone cell layers in maize endosperm. In this study, we investigated the structure and function of a Nicotiana benthamiana CHMP1 homolog designated NbCHMP1. NbCHMP1 encodes a small protein with a bipartite nuclear localization signal at its N-terminus, and good homology with the corresponding genes from diverse plants and animals. NbCHMP1 mRNA was present at comparable levels in stems, roots, flowers, and leaves. A GFP fusion of the full length NbCHMP1 protein was localized to the cytosol in distinct structures, while a GFP fusion of its N-terminal 80 aa was targeted to the nucleus, suggesting dual-targeting of NbCHMP1 in plants. Overexpression of NbCHMP1 in yeast did not affect its growth and the expressed protein was present in the cytosol in particulate form. Virus-induced gene silencing of NbCHMP1 resulted in subtle alterations of leaf morphology and color, without significantly affecting plant viability or development. Thus the CHMP1 homolog apparently does not play an essential role in the development of the vegetative tissues of N. benthamiana, in contrast to the essential role of sail in formation of the aleurone cell layers during maize endosperm development.

Amino Acid Sequence↗

PubMed2004

EST and microarray analyses of pathogen-responsive genes in hot pepper (Capsicum annuum L.) non-host resistance against soybean pustule pathogen (Xanthomonas axonopodis pv. glycines).

Large-scale single-pass sequencing of cDNA libraries and microarray analysis have proven to be useful tools for discovering new genes and studying gene expression. As a first step in elucidating the defense mechanisms in hot pepper plants, a total of 8,525 expressed sequence tags (ESTs) were generated and analyzed in silico. The cDNA microarray analysis identified 613 hot pepper genes that were transcriptionally responsive to the non-host soybean pustule pathogen Xanthomonas axonopodis pv. glycines ( Xag). Several functional types of genes, including those involved in cell wall modification/biosynthesis, transport, signaling pathways and divergent defense reactions, were induced at the early stage of Xag infiltration. In contrast, genes encoding proteins that are involved in photosynthesis, carbohydrate metabolism and the synthesis of chloroplast biogenetic proteins were down-regulated at the late stage of Xag infiltration. These expression profiles share common features with the expression profiles elicited by other stresses, such as fungal challenge, wounding, cold, drought and high salinity. However, we also identified several novel transcription factors that may be specifically involved in the defense reaction of the hot pepper. We also found that the defense reaction of the hot pepper may involve the deactivation of gibberellin. Furthermore, many genes encoding proteins with unknown function were identified. Functional analysis of these genes may broaden our understanding of non-host resistance. This study is the first report of large-scale sequencing and non-host defense transcriptome analysis of the hot pepper plant species. (The sequence data in this paper have been submitted to the dbEST and GenBank database under the codes 10227604-10236595 and BM059564-BM068555, respectively. Additional information is available at http://plant.pdrc.re.kr/ks200201/pepper.html).

Capsicum↗

PubMed2004

Phytocalpain controls the proliferation and differentiation fates of cells in plant organ development.

Calpain, a calcium-dependent cysteine protease, plays an essential role in basic cellular processes in animal cells, including cell proliferation, apoptosis, and differentiation. NbDEK encodes the calpain homolog of N. benthamiana. In this study, virus-induced gene silencing (VIGS) of NbDEK resulted in arrested organ development and hyperplasia in all the major plant organs examined. The epidermal layers of the leaves and stems were covered with hyperproliferating cell masses, and stomata and trichome development was severely inhibited. During flower development, a single dome-like structure was grown from the flower meristem to generate a large cylinder-shaped flower lacking any floral organs. At the cellular level, cell division was sustained in tissues that were otherwise already differentiated, and cell differentiation was severely hampered. NbDEK is ubiquitously expressed in all the plant tissues examined. In the abnormal organs of the NbDEK VIGS lines, protein levels of D-type cyclins (CycD)2, CycD3, and proliferating cell nuclear antigen (PCNA) were greatly elevated, and transcription of E2F (E2 promoter binding factor), E2F-regulated genes, retinoblastoma (Rb), and KNOTTED1 (KN1)-type homeobox genes was also stimulated. These results suggest that phytocalpain is a key regulator of cell proliferation and differentiation during plant organogenesis, and that it acts partly by controlling the CycD/Rb pathway.

Amino Acid Sequence↗