Biomedical subjects

Jiansheng Liang

Publications and source records attributed to Jiansheng Liang.

7 recordsLinked to original sources

PubMed2025

Genomic context-dependent roles of 5-hydroxymethylcytosine in regulating gene expression during rice drought response.

DNA methylation (5-methylcytosine, 5mC) is a key epigenetic regulator of genome stability and stress adaptation in plants. However, the functional role of its oxidative derivative, 5-hydroxymethylcytosine (5hmC), remains poorly understood in plant systems, largely due to its low abundance and unresolved enzymatic origins. Here, we integrated ACE-seq (APOBEC-coupled epigenetic sequencing) with an optimized Tn5mC-seq (transposase-based library preparation in the context of whole-genome bisulfite sequencing, WGBS) approach to generate the first single-base resolution map of 5hmC in rice (Oryza sativa), unveiling its stress-responsive dynamics and regulatory interplay with 5mC during drought adaptation. Genome-wide profiling revealed a basal 5hmC level of ~0.03 (defined as the ratio of C/(C + T) at each site), with drought triggering a pronounced reduction in 5hmC abundance and locus number, followed by incomplete recovery post-rehydration. Unlike 5mC, which accumulates in heterochromatin, 5hmC preferentially localized to euchromatic regions, including promoters, exons, and intergenic elements, and exhibited enrichment at ABA-responsive transcription factors (e.g., OsATAF1, bZIP50). Strikingly, drought induced an antagonistic relationship between 5hmC and 5mC, with the latter increasing globally to reinforce transposon silencing. Multi-omics analyses demonstrated that 5hmC depletion in promoters correlated with transcriptional downregulation, while its accumulation in gene bodies (notably 5'-UTRs) suppressed stress-responsive genes. These findings highlight 5hmC's bifunctional regulatory capacity, contingent on genomic context, and its role in balancing transcriptional plasticity with genome stability during stress. Our work establishes 5hmC as a dynamic epigenetic mark in plant environmental adaptation and provides a foundation for leveraging DNA hydroxymethylation in crop resilience engineering.

Oryza↗

PubMed2006

RACK1 mediates multiple hormone responsiveness and developmental processes in Arabidopsis.

The scaffold protein RACK1 (Receptor for Activated C Kinase 1) serves as an integrative point for diverse signal transduction pathways. The Arabidopsis genome contains three RACK1 orthologues, however, little is known about their functions. It is reported here that one member of this gene family, RACK1A, previously identified as the Arabidopsis homologue of the tobacco arcA gene, mediates hormone responses and plays a regulatory role in multiple developmental processes. RACK1A expresses ubiquitously in Arabidopsis. Loss-of-function mutations in RACK1A confer defects in multiple developmental processes including seed germination, leaf production, and flowering. rack1a mutants displayed reduced sensitivity to gibberellin and brassinosteroid in seed germination, hypersensitivity to abscisic acid in seed germination and early seedling development, and hyposensitivity to auxin in adventitious and lateral root formation. These results provide the first genetic evidence that RACK1A is involved in multiple signal transduction pathways.

Amino Acid Sequence↗

PubMed2006

Overexpression of the regulator of G-protein signalling protein enhances ABA-mediated inhibition of root elongation and drought tolerance in Arabidopsis.

Regulator of G-protein signalling (RGS) proteins identified recently in Arabidopsis have been involved in the regulation of several physiological processes, but largely nothing is known about their roles at both the physiological and the molecular level. In the experiments reported here, the overexpression approach was used to present evidence that RGS1 protein plays critical roles in plant development and in modulating abscisic acid (ABA) and drought stress signal transduction. RGS1 affected the shapes of leaves, the development of floral buds, the elongation of stems, siliques, and hypocotyls, and the time of flowering. Post-germination growth was inhibited by 1 microM ABA, and root growth was hypersensitive to ABA for 35S-RGS1 transgenic plants. RGS1 overexpression conferred more drought tolerance to transgenic plants, as compared with the wild type (Columbia). Reverse transcription-PCR (RT-PCR) results indicated that RGS1 overexpresssion significantly stimulated the expression of NCED and ABA2, that encode two key enzymes catalysing ABA biosynthesis. Furthermore, the expression of several stress-regulated genes was either up- or down-regulated in RGS1-overexpressing transgenic plants. Combining the results above with previous results, it is suggested that RGS1 exerted its effects on plant responsiveness to ABA and drought tolerance largely through changing the expression either of genes responsible for ABA biosynthesis, which leads to changes in endogenous ABA levels, or of stress-responsive genes.

Abscisic Acid↗

PubMed2005

The regulator of G-protein signaling proteins involved in sugar and abscisic acid signaling in Arabidopsis seed germination.

The regulator of G-protein signaling (RGS) proteins, recently identified in Arabidopsis (Arabidopsis thaliana; named as AtRGS1), has a predicted seven-transmembrane structure as well as an RGS box with GTPase-accelerating activity and thus desensitizes the G-protein-mediated signaling. The roles of AtRGS1 proteins in Arabidopsis seed germination and their possible interactions with sugars and abscisic acid (ABA) were investigated in this study. Using seeds that carry a null mutation in the genes encoding RGS protein (AtRGS1) and the alpha-subunit (AtGPA1) of the G protein in Arabidopsis (named rgs1-2 and gpa1-3, respectively), our genetic evidence proved the involvement of the AtRGS1 protein in the modulation of seed germination. In contrast to wild-type Columbia-0 and gpa1-3, stratification was found not to be required and the after-ripening process had no effect on the rgs1-2 seed germination. In addition, rgs1-2 seed germination was insensitive to glucose (Glc) and sucrose. The insensitivities of rgs1-2 to Glc and sucrose were not due to a possible osmotic stress because the germination of rgs1-2 mutant seeds showed the same response as those of gpa1-3 mutants and wild type when treated with the same concentrations of mannitol and sorbitol. The gpa1-3 seed germination was hypersensitive while rgs1-2 was less sensitive to exogenous ABA. The different responses to ABA largely diminished and the inhibitory effects on seed germination by exogenous ABA and Glc were markedly alleviated when endogenous ABA biosynthesis was inhibited. Hypersensitive responses of seed germination to both Glc and ABA were also observed in the overexpressor of AtRGS1. Analysis of the active endogenous ABA levels and the expression of NCED3 and ABA2 genes showed that Glc significantly stimulated the ABA biosynthesis and increased the expression of NCED3 and ABA2 genes in germinating Columbia seeds, but not in rgs1-2 mutant seeds. These data suggest that AtRGS1 proteins are involved in the regulation of seed germination. The hyposensitivity of rgs1-2 mutant seed germination to Glc might be the result of the impairment of ABA biosynthesis during seed germination.

Abscisic Acid↗

PubMed2003

A seven-transmembrane RGS protein that modulates plant cell proliferation.

G protein-coupled receptors (GPCRs) at the cell surface activate heterotrimeric G proteins by inducing the G protein alpha (Galpha) subunit to exchange guanosine diphosphate for guanosine triphosphate. Regulators of G protein signaling (RGS) proteins accelerate the deactivation of Galpha subunits to reduce GPCR signaling. Here we identified an RGS protein (AtRGS1) in Arabidopsis that has a predicted structure similar to a GPCR as well as an RGS box with GTPase accelerating activity. Expression of AtRGS1 complemented the pheromone supersensitivity phenotype of a yeast RGS mutant, sst2Delta. Loss of AtRGS1 increased the activity of the Arabidopsis Galpha subunit, resulting in increased cell elongation in hypocotyls in darkness and increased cell production in roots grown in light. These findings suggest that AtRGS1 is a critical modulator of plant cell proliferation.

Alleles↗

PubMed2001

Grain sink strength may be related to the poor grain filling of indica-japonica rice (Oryza sativa) hybrids.

The physiological and biochemical factors contributing to poor grain filling of indica-japonica rice (Oryza sativa L.) hybrids were studied by analyzing the role of grain sink strength in dry matter accumulation of grains of two types of rice cultivars, Yayou 2 (an indica-japonica hybrid) and Yanjing 2 (a japonica cultivar). Carbon dioxide enrichment and plant hormone application were imposed at anthesis and the number of endosperm cells, dry matter accumulation and the activities of some sugar-metabolizing enzymes of grains were measured during grain filling. In Yayou 2, strong-potential grains (SPGs) accumulated dry weight much earlier than weak-potential grains (WPGs), but this difference was not obvious for Yanjing 2. Carbon dioxide enrichment imposed after heading significantly stimulated dry matter accumulation of WPGs of Yayou 2, but had little influence on WPGs of Yanjing 2 and SPGs of both cultivars. Leaf sheath dry matter decreased steadily in both cultivars during early stages of grain filling and accumulated during the later stages. Carbon dioxide enrichment increased leaf sheath dry matter. Dry matter accumulated by grains was linearly related to the increases in endosperm cell numbers and the activities of sucrose synthase (SS) and ADP-glucose pyrophosphorylase (AGPase) in SPGs and WPGs of both cultivars. Application of either 6-benzyladenine or abscisic acid had no significant influences on both endosperm cell number and grain dry matter accumulation. These results suggest that grain sink strength, determined by both cell numbers, SS and AGPase activities in the endosperm control the dry matter accumulation of grains.

Journal Article↗

PubMed1999

Can differences in root responses to soil drying and compaction explain differences in performance of trees growing on landfill sites?

Two tropical woody species, Acacia confusa Merrill and Litsea glutinosa (Lour.) C.B. Robinson, were grown under controlled conditions in PVC pipes filled with John Innes No. 2 soil. To investigate root distribution, physiological characteristics and hydraulic conductivity, four soil treatments were imposed-well-watered and noncompacted (control), well-watered and compacted; unwatered and noncompacted, and unwatered and compacted. In L. glutinosa, rooting depth and root elongation were severely restricted when soil bulk density increased from around 1.12 to 1.62 g cm(-3), whereas soil compaction had little effect on these parameters in A. confusa. As soil drying progressed, root water potential and osmotic potential declined more slowly in L. glutinosa than in A. confusa. Both the soil drying and compaction treatments significantly stimulated the accumulation of root abscisic acid (ABA) in both species. Soil drying damaged the root cell membrane of A. confusa, but had little influence on the root cell membrane of L. glutinosa. Soil drying had a greater effect on root hydraulic conductivity (L(p)) in L. glutinosa than in A. confusa, whereas the effect of soil compaction on L(p) was less in L. glutinosa than in A. confusa. Soil drying enhanced the effects of soil compaction on root L(p). We conclude that soil drying and compaction have large species-specific effects on the distribution, growth and physiology of roots. The relationships of these root properties to the species' ability to tolerate unfavorable soil conditions were examined.

Journal Article↗