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SPINDLY, a tetratricopeptide repeat protein involved in gibberellin signal transduction in Arabidopsis.

Gibberellins (GAs) are a major class of plant hormones that control many developmental processes, including seed development and germination, flower and fruit development, and flowering time. Genetic studies with Arabidopsis thaliana have identified two genes involved in GA perception or signal transduction. A semidominant mutation at the GIBBERELLIN INSENSITIVE (GAI) locus results in plants resembling GA-deficient mutants but exhibiting reduced sensitivity to GA. Recessive mutations at the SPINDLY (SPY) locus cause a phenotype that is consistent with constitutive activation of GA signal transduction. Here we show that a strong allele of spy is completely epistatic to gai, indicating that SPY acts downstream of GAI. We have cloned the SPY gene and shown that it encodes a new type of signal transduction protein, which contains a tetratricopeptide repeat region, likely serving as a protein interaction domain, and a novel C-terminal region. Mutations in both domains increase GA signal transduction. The presence of a similar gene in Caenorhabditis elegans suggests that SPY represents a class of signal transduction proteins that is present throughout the eukaryotes.

Alleles↗

Regulation of Gene Expression by Ethylene in Wild-Type and rin Tomato (Lycopersicon esculentum) Fruit.

Levels of ethylene biosynthesis and ethylene-inducible gene expression in wild-type tomato (Lycopersicon esculentum) fruit and in nonripening fruit from the tomato mutant rin (ripening inhibitor) were compared in order to investigate the mechanism of ethylene action. Whereas wild-type tomato fruit dramatically increase the rate of ethylene biosynthesis at the onset of ripening, rin fruit constitutively produce ethylene at a low basal level. We have compared the mRNA levels and transcription rates of four cloned ethylene-inducible genes (JE Lincoln, S Cordes, E Read, RL Fischer 1987 Proc Natl Acad Sci USA 84: 2793-2797) during wild-type and rin fruit development. In wild-type fruit, both mRNA levels and transcription rates of these genes increase. The effect of the rin mutation on gene expression is different for each ethylene-inducible gene. In one case expression is completely suppressed, while in other instances it is either partially inhibited or relatively unaffected by the mutation. The mRNA levels of each of these genes in response to exogenous ethylene in rin fruit was also measured. The mRNAs for all four genes accumulate to similar levels in both ethylene treated rin and ethylene treated wild-type fruit. These results are discussed with regard to the response of plants to ethylene hormone at the level of gene expression.

Journal Article↗

A contribution to our knowledge of ginseng.

The Chinese people discovered ginseng and used it as a revitalizing agent since time immemorial. They are still the world's major consumers of this plant drug. The commercial product of ginseng comes from two species of the genus Panax in the family Araliaceae. These species are P. ginseng C. A. Meyer which is the source plant of the Chinese, Korean and Japanese brands of ginseng, and P. quinquefolius L., which is the source of American ginseng. Phytogeographically, ginseng demonstrates the classical bicentric pattern of plant distribution, with closely related species in eastern Asia and in eastern North America. Ecologically, ginseng is an undergrowth of hardwood mixed deciduous forest. It prefers the northern or the northeastern slope of a hill. Species of the genus Tilia are good indicators of the proper environmental condition for the growth of ginseng. Morphologically, ginseng is a perennial herb with fleshy root, a single annual stem bearing a whorl of palmately compound leaves, and a terminal simple umbel of small 5-merous flowers. The flowers are soon followed by pea-sized fruits developed from inferior ovaries. The fruits are red when ripe. Ginseng is propagated by seed. The commercial products of ginseng consist primarily of roots 2-20 years old. Within this age range, the older the root the higher the market value, provided they are grown in proper conditions. The methods of curing the roots change the color and shape of the products. Chinese ginseng is prepared from roots bleached, boiled, steamed, or sugared in curing. The cultural background for the uses of ginseng by the Chinese people is explained. Ginseng may be used alone in the form of tea, powder, or as a masticatory. It is also used in combination with other drugs of animal, mineral, or plant origin. Forty-two recipes are selected from Pen-ts'oa kang-mu and translated into English for the first time to show the various ways by which ginseng is used in traditional Chinese medicine. A systematic summary of the companion plant drugs of ginseng is presented in the form of a table, showing the distribution of the species in the plant kingdom. The scientific names of the species are given in full.

Agriculture↗

Fruit developmental regulation of the kiwifruit actinidin promoter is conserved in transgenic petunia plants.

We have examined the expression of actinidin, a cysteine protease found in kiwifruit, over the course of fruit development. Protease activity was first seen in fruit that had reached about half their final weight, and rose to high levels at harvest. The 5'-flanking region (nucleotides -1301 to +58) of a kiwifruit actinidin gene was fused to the beta-glucuronidase (GUS)-coding region, and the chimaeric gene was introduced into transgenic petunia plants. Induction of the GUS gene was observed during the later stages of seed pod development, closely resembling the pattern of actinidin induction in fruit tissues of kiwifruit. Some GUS expression was also detected in the vascular system of the receptacle, leaves, stems and roots. A shorter promoter fragment consisting of nucleotides -115 to +58 conferred similar spatial and temporal regulation in some of the transgenic plants.

Base Sequence↗

Ecology and economic impact of two plant bugs (Hemiptera: Miridae) in commercial vineyards.

The current study investigated the seasonal phenology, spatial distribution, feeding damage and economic impact of two plant bugs, Lygocoris inconspicuous Knight and Taedia scrupeus Say, in commercial vineyards. For both plant bugs, densities of nymphs were higher on vines located near the edge of woodlots rather than in the interior of vineyards, which may be attributed to the presence of wild vines and other alternate host-plants in wooded areas. Nymphs of both species fed on apical leaves and developing fruit clusters of vine shoots, initiating development after swelling of buds in the spring and reaching the adult stage when vines were in bloom. Confining high densities of L. inconspicuous (10 nymphs) on individual shoots early in the season resulted in significant reduction of the number of fruit clusters per shoot, even when feeding was restricted to short (7 d) duration; the average weight of fruit clusters, in contrast, was not affected to a large extent by feeding activity of nymphs. An experiment evaluating the impact of low density of L. inconspicuous (0-0.3 nymphs per shoot) indicated a marginally significant negative relationship between density of nymphs and average weight of fruit clusters. Control measures may be economically justified when population density exceeds a combined threshold of one nymph of either L. inconspicuous or T. scrupeus per 10 shoots of vines.

Animals↗

Developmentally regulated expression of two MADS-box genes, MdMADS3 and MdMADS4, in the morphogenesis of flower buds and fruits in apple.

Two MADS-box genes, MdMADS3 and MdMADS4, were isolated from the apple (Malus x domestica Borkh.) cultivar Fuji, and their spatial and temporal expression patterns were studied during morphological differentiation of the flower buds and the fruits. Both MdMADS3 and MdMADS4 showed high sequence similarities to FBP2 from petunia, TM5 from tomato, and AGL2, AGL4 from Arabidopsis. Although MdMADS3 was expressed in the inner three whorls of the floral primordium, its expression was hardly detectable in developing fruit. The second gene, MdMADS4, was ubiquitously expressed in the inflorescence meristem, floral meristem, all four floral organs, and fruit. Moreover, MdMADS4 expression was high in the vascular bundles assigned to the floral tube and the carpellary vascular bundles in fruit at early developmental stages. The MdMADS4 transcript also accumulated in embryos of the developing seeds. These results suggest that MdMADS3 and MdMADS4 are involved in different functions, and that MdMADS4 may function in the important events controlling flower and fruit development.

Amino Acid Sequence↗

Functional heterostyly in Tylosema esculentum (Caesalpinioideae).

Tylosema esculentum is a long-lived perennial species endemic to arid areas of southern Africa. Its potential as a crop species has long been recognized as a result of the high oil and protein content of its seeds. The reproductive biology and breeding systems of the species were investigated in wild and experimental populations growing in Botswana. Field observations confirmed that the species is heterostylous with the pistil and anthers exhibiting reciprocal heights in the two morphs, although pollen size and sculpturing do not vary. The wet, nonpapillate stigma characteristic of the species is the first to be reported in the Caesalpinioideae. In vivo and in vitro diallel crossing experiments demonstrated that a diallelic self-incompatability system exists in T. esculentum. The major site of pollen tube inhibition in the intramorph crosses was found to be in the style. This is the first report of functional heterostyly in the Fabaceae and of a confirmed self-incompatibility system in the Caesalpinioideae. Three separate lines of evidence, the monitoring of fruit development in open-pollinated plants, fruit set in diallel crossing experiments, and observations made in wild populations, demonstrated that fruit set and, by implication, seed set, are very low in this species. Floral abscission was a major limitation to the production of mature pods but there were also significant losses at other developmental stages of fruit production. The results suggest that low seed set may be an adaptation of the species to an environment in which rainfall is scarce.

Alleles↗

Developmental regulation of peach ACC oxidase promoter--GUS fusions in transgenic tomato fruits.

A genomic DNA sequence (PpACO1) encoding 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) from peach (Prunus persica L. Batsch cv. Loring) was isolated. It has four exons interrupted by three introns and 2.9 kb of flanking region 5' of the translational start codon. Previous work with the cDNA demonstrated that accumulation of the peach ACO message correlated with increasing amounts of ethylene synthesized by the fruit as they ripened. To identify regulatory elements in the peach ACC oxidase gene, chimeric fusions between 403, 610, 901, 1319, 2141, and 2919 bp of the 5' flanking region of the PpACO1 sequence and the beta-glucuronidase (GUS) coding sequence were constructed and used to transform tomato (Lycopersicon esculentum [Mill] cv. Pixie). Fruits from the various promoter lines were analysed for GUS expression by histochemical GUS staining, GUS quantitative enzyme activity determination, and measuring the relative amounts of GUS mRNA. Constructs with the smallest promoter of 403 bp had significant GUS expression in fruit, but not in other tissues, indicating the presence of a region that affects tissue-specific expression. An increase in GUS expression was observed with promoters longer than 901 bp, indicating an enhancer region between -1319 and -901. The full-length promoter of 2919 bp directed GUS expression in the green stage of fruit development, and increased GUS expression as fruit matured, indicating a regulatory region between -2919 and -2141 that controls the temporal expression of the gene in fruit. Only the full-length promoter sequence demonstrated responsiveness to ethylene.

Amino Acid Oxidoreductases↗

Molecular cloning and expression of cDNAs encoding alcohol dehydrogenases from Vitis vinifera L. during berry development.

Three full-length cDNAs (VvAdh1, VvAdh2, and VvAdh3) encoding alcohol dehydrogenases (EC 1.1.1.1) were obtained from grape berries (Vitis vinifera L.) by means of PCR and RACE. Pairwise comparisons at the nucleotide level showed that the three cDNAs displayed strong homology in the coding region, but were highly divergent in the 5' and 3' untranslated regions. VvAdh1 and VvAdh2 corresponded to the two previously characterised Adh genes from grapevine, but VvAdh3 was unrelated to known grapevine Adh sequences. The two first cDNAs presented a single ORF of 380 amino acids, whereas the last one has two additional residues. Moreover, the three encoded polypeptides possessed the 22 residues strictly conserved between Adh from different kingdoms. Expression pattern of the individual isogenes was investigated during fruit development. Specific primers were designed, and quantitative RT-PCR experiments were performed to increase the sensitivity of detecting isogenes with a low expression level. Results presented here revealed different developmental regulation of the three Adh isogenes during fruit ripening. VvAdh1 and VvAdh3 transcripts were temporarily accumulated in young, developing berry, whereas VvAdh2 was overexpressed later in fruit development, from the onset of ripening (véraison). Expression analysis also indicated that VvAdh2 accounted for most of the Adh mRNAs present in berries during development. The increased ADH activity detected in berries correlated with the expression pattern of VvAdh2 transcripts. The VvAdh2 and VvAdh3 encoded enzymes were purified from overexpressing E. coli cells. Comparison of kinetic properties of the two ADH enzymes showed a difference in affinity with either ethanol or acetaldehyde as substrates. Significance of multiple Adh expressed in berries is discussed.

Journal Article↗

A family of polyketide synthase genes expressed in ripening Rubus fruits.

Quality traits of raspberry fruits such as aroma and color derive in part from the polyketide derivatives, benzalacetone and dihydrochalcone, respectively. The formation of these metabolites during fruit ripening is the result of the activity of polyketide synthases (PKS), benzalcetone synthase and chalcone synthase (CHS), during fruit development. To gain an understanding of the regulation of these multiple PKSs during fruit ripening, we have characterized the repertoire of Rubus PKS genes and studied their expression patterns during fruit ripening. Using a PCR-based homology search, a family of ten PKS genes (Ripks1-10) sharing 82-98% nucleotide sequence identity was identified in the Rubus idaeus genome. Low stringency screening of a ripening fruit-specific cDNA library, identified three groups of PKS cDNAs. Group 1 and 2 cDNAs were also represented in the PCR amplified products, while group 3 represented a new class of Rubus PKS gene. The Rubus PKS gene-family thus consists of at least eleven members. The three cDNAs exhibit distinct tissue-specific and developmentally regulated patterns of expression. RiPKS5 has high constitutive levels of expression in all organs, including developing flowers and fruits, while RiPKS6 and RiPKS11 expression is consistent with developmental and tissue-specific regulation in various organs. The recombinant proteins encoded by the three RiPKS cDNAs showed a typical CHS-type PKS activity. While phylogenetic analysis placed the three Rubus PKSs in one cluster, suggesting a recent duplication event, their distinct expression patterns suggest that their regulation, and thus function(s), has evolved independently of the structural genes themselves.

Amino Acid Sequence↗

AUXIN RESPONSE FACTOR8 is a negative regulator of fruit initiation in Arabidopsis.

Fruit and seed formation in plants is normally initiated after pollination and fertilization, and, in the absence of fertilization, flowers senesce. In the Arabidopsis thaliana mutant fruit without fertilization, a mutation in AUXIN RESPONSE FACTOR8 (ARF8) results in the uncoupling of fruit development from pollination and fertilization and gives rise to seedless (parthenocarpic) fruit. Parthenocarpy was confirmed in two additional recessive alleles and was caused by mutations within the coding region of ARF8. Genetic experiments indicate that ARF8 acts as an inhibitor to stop further carpel development in the absence of fertilization and the generation of signals required to initiate fruit and seed development. Expression of ARF8 was found to be regulated at multiple levels, and transcriptional autoregulation of ARF8 was observed. Analysis of plants transformed with a transcriptional P(ARF8):beta-glucuronidase (GUS) construct or a translational ARF8:GUS fusion construct displayed distinct developmental regulation of the reporter in floral tissues involved in pollination and fertilization and in the carpel wall. After fertilization, the level of GUS activity declined in the developing seed, while in unfertilized ovules that are destined to senesce, ARF8:GUS expression spread throughout the ovule. This is consistent with a proposed role for ARF8 in restricting signal transduction processes in ovules and growth in pistils until the fruit initiation cue.

Alleles↗

Organ-specific differential regulation of a promoter subfamily for the ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit genes in tomato.

The tomato (Lycopersicon esculentum) gene family for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RBCS) has been investigated to determine the role of promoter regions and DNA-protein interactions in the differential organ-specific transcription of individual genes. Transgenic plants expressing RBCS-promoter-beta-glucuronidase fusion genes have confirmed that promoter fragments ranging from 0.6 to 3.0 kb of the RBCS1, RBCS2, and RBCS3A genes were sufficient to confer the temporal, organ-specific, and differential expression pattern observed for the endogenous genes. The individual temporal and organ-specific beta-glucuronidase enzyme activities closely reflect the qualitative and quantitative transcription activities of the respective RBCS genes, including the strongly reduced activity of RBCS3A (L.A. Wanner, W. Gruissem [1991] Plant Cell 3: 1289-1303). In particular, tissue-specific activity of all three promoters is similar in developing fruit, with high activity in the locular tissue and extremely reduced activity in the pericarp. This specific pattern of gene activity was further substantiated by in situ analysis of RBCS mRNA levels. Together, the data suggest an interesting correlation between RBCS gene activity and sink strength in different fruit tissues. DNA-protein interaction studies have revealed a novel fruit-specific DNA-binding protein called FBF that specifically interacts with a sequence element directly upstream of the G-box in the RBCS3A promoter. FBF binding thus correlates with the reduced activity of this promoter in developing tomato fruit, rendering it a candidate for a fruit-specific negative regulator of transcription in tomato.

Base Sequence↗

A cDNA from grapevine (Vitis vinifera L.), which shows homology to AGAMOUS and SHATTERPROOF, is not only expressed in flowers but also throughout berry development.

An AGAMOUS/SHATTERPROOF homologue (Vvmads1) was isolated from grapevine by differential display between berry and leaf mRNA. The predicted protein sequence of the full-length clone shows a high degree of homology to PLENA (77% identity) and to SHP1 and SHP2 (75% and 74% identity respectively), and is grouped with AGAMOUS/PLENA homologues when the conserved MADS and K domains are compared. Vvmads1 is expressed only in the later stages of flower development and throughout berry development, although expression is reduced after ripening commenced. When Vvmads1 was over-expressed in tobacco, the resulting plants display altered morphologies in the outer two floral whorls. In the most extreme cases, the inner whorls were surrounded by a carpelloid structure created by the modified sepals. Within these sepals were petals which had been split into sections and which were attached at the base of the flower by structures with the appearance of filaments. The results of this study suggest that Vvmads1 has a regulatory role in flower development before fertilisation and a role in fruit development after fertilisation.

AGAMOUS Protein, Arabidopsis↗

Molecular cloning and organ-specific expression of three isoforms of tomato ADP-glucose pyrophosphorylase gene.

We isolated three cDNAs encoding different isoforms of ADP-glucose pyrophosphorylase (AGP) large submits from tomato plants. Three clones, designated AgpL1, AgpL2, and AgpL3 were 2019, 2105, and 1850bp, respectively. The clones had a long, uninterrupted open reading frame with a start codon at the 5' region and different copies of polyadenylation signal (AATAAA) at the 3' region, deriving 57-58kDa polypeptides. Sequence comparison and phylogenetic analysis revealed that the three isoforms represented different types of AGP large subunits, AgpL1 was strongly expressed in stems and weakly in roots. Accumulation of AgpL1 transcripts was found even in unpollinated ovaries and sustained at the early stages of fruit development. ApgL2 was expressed in roots and fruits. AgpL3 was exclusively expressed in leaves. The present study suggests that the three isoforms of tomato AGP large subunits are organ-specific in their expressions.

Amino Acid Sequence↗

Influence of harvest date within the season and cold storage on cherimoya fruit ripening.

Cherimoya ripening with and without prior storage at 8 degrees C was studied in fruit harvested on early- (EH), mid- (MH), and late-season (LH) dates. Most of the differences in the ripening behavior were observed between EH cherimoyas and fruit from the other two harvest dates. During ripening of nonstored fruit, the increases in ethylene production and respiration rates and in soluble sugars and organic acids contents were faster in EH than in the other fruits (which ripened 1 day later). These differences could be due to variations in the physiological stage at harvest as a result of the different heat units (degree/month) accumulated in the last month of fruit development. During ripening of cold-stored fruit the differences in the time to the onset of the increase in ethylene production and in the accumulation of malic and citric acid were minimized, especially after longer storage times, and the relationship of harvest date with the increases in respiration rate was lost. Glucose and fructose accumulation was reduced by prior cold storage, especially after longer storage duration and in MH and LH fruit, but sucrose hydrolysis was almost complete, as in nonstored fruit. It is suggested that glucose and fructose accumulation is more sensitive to low temperature than sucrose metabolism and that this differential sensitivity is more marked in MH and LH cherimoyas. The time to ripen was inversely related to prior cold storage duration and was dependent on harvest date: the later the harvest date, the longer storage time it took to shorten subsequent ripening.

Cold Temperature↗

Genetic engineering of parthenocarpic plants.

Transgenic tobacco and eggplants expressing the coding region of the iaaM gene from Pseudomonas syringae pv. savastanoi, under the control of the regulatory sequences of the ovule-specific DefH9 gene from Antirrhinum majus, showed parthenocarpic fruit development. Expression of the DefH9-iaaM chimeric transgene occurs during flower development in both tobacco and eggplant. Seedless fruits were produced by emasculated flowers. When pollinated, the parthenocarpic plants produced fruits containing seeds. In eggplant, the genetic manipulation allowed fruit set and growth under environmental conditions prohibitive for fruit setting in the untransformed line, which did not set fruit at all. Under normal environmental conditions, production of marketable fruits took place from pollinated and unpollinated transgenic flowers, while flowers of untransformed control plants did produce fruits of marketable size only from fertilized flowers.

Chimera↗

Inhibition of chloroplastic fructose 1,6-bisphosphatase in tomato fruits leads to decreased fruit size, but only small changes in carbohydrate metabolism.

A potato (Solanum tuberosum L.) cDNA coding for the chloroplastic isoform of fructose 1,6-bisphosphatase (cp-FBPase) was utilized to repress its activity in tomatoes (Lycopersicon esculentum Mill.) using antisense techniques. The patatin B33 promoter was used to ensure fruit specificity of the antisense effect. Transgenic plants were isolated in which fructose 1,6-bisphosphatase activity was reduced by more than 50% of the control in green fruits. Immunoblots indicated that the plastidial isoform was almost completely eliminated in the most strongly inhibited lines. Fruits of the transgenic plants were analyzed for levels of metabolites during fruit development. Glucose and fructose concentrations were increased in green fruits in the transgenic lines, but unchanged at later stages of development. The sucrose concentration was low, and was not significantly altered in the transgenic lines. There was net degradation of starch over the developmental period, but the starch content was not decreased. In green fruit the levels of hexose phosphates were unchanged, whilst the level of 3-phosphoglyceric acid was significantly increased in one line. Most importantly the deduced ratio of hexose phosphate to 3-phosphoglyceric acid decreased, consistent with an in vivo inhibition of fructose 1,6-bisphosphatase activity. One consequence of this reduction of in vivo activity of cp-FBPase was that the average weight of fully ripe fruits was significantly decreased by up to 20% in all transgenic lines in comparison with the control.

Carbohydrate Metabolism↗