Zexiong Chen

Bio: Zexiong Chen is an academic researcher from Chongqing University. The author has contributed to research in topics: Biology & Medicine. The author has an hindex of 7, co-authored 18 publications receiving 116 citations.

Genome-wide identification and characterization of bHLH family genes from Ginkgo biloba.

Abstract: Basic helix-loop-helix (bHLH) proteins, one of the most important and largest transcription factor family in plants, play important roles in regulating growth and development, stress response. In recent years, many bHLH family genes have been identified and characterized in woody plants. However, a systematic analysis of the bHLH gene family has not been reported in Ginkgo biloba, the oldest relic plant species. In this study, we identifed a total of 85 GbbHLH genes from the genomic and transcriptomic databases of G. biloba, which were classified into 17 subfamilies based on the phylogenetic analysis. Gene structures analysis indicated that the number of exon-intron range in GbbHLHs from 0 to 12. The MEME analysis showed that two conserved motifs, motif 1 and motif 2, distributed in most GbbHLH protein. Subcellular localization analysis exhibited that most GbbHLHs located in nucleus and a few GbbHLHs were distributed in chloroplast, plasma membrane and peroxisome. Promoter cis-element analysis revealed that most of the GbbHLH genes contained abundant cis-elements that involved in plant growth and development, secondary metabolism biosynthesis, various abiotic stresses response. In addition, correlation analysis between gene expression and flavonoid content screened seven candidate GbbHLH genes involved in flavonoid biosynthesis, providing the targeted gene encoding transcript factor for increase the flavonoid production through genetic engineering in G. biloba.

Comparative transcriptome analysis revealing the potential mechanism of seed germination stimulated by exogenous gibberellin in Fraxinus hupehensis

Abstract: Fraxinus hupehensis is an endangered tree species that is endemic to in China; the species has very high commercial value because of its intricate shape and potential to improve and protect the environment. Its seeds show very low germination rates in natural conditions. Preliminary experiments indicated that gibberellin (GA3) effectively stimulated the seed germination of F. hupehensis. However, little is known about the physiological and molecular mechanisms underlying the effect of GA3 on F. hupehensis seed germination. We compared dormant seeds (CK group) and germinated seeds after treatment with water (W group) and GA3 (G group) in terms of seed vigor and several other physiological indicators related to germination, hormone content, and transcriptomics. Results showed that GA3 treatment increases seed vigor, energy requirements, and trans-Zetain (ZT) and GA3 contents but decreases sugar and abscisic acid (ABA) contents. A total of 116,932 unigenes were obtained from F. hupehensis transcriptome. RNA-seq analysis identified 31,856, 33,188 and 2056 differentially expressed genes (DEGs) between the W and CK groups, the G and CK groups, and the G and W groups, respectively. Up-regulation of eight selected DEGs of the glycolytic pathway accelerated the oxidative decomposition of sugar to release energy for germination. Up-regulated genes involved in ZT (two genes) and GA3 (one gene) biosynthesis, ABA degradation pathway (one gene), and ABA signal transduction (two genes) may contribute to seed germination. Two down-regulated genes associated with GA3 signal transduction were also observed in the G group. GA3-regulated genes may alter hormone levels to facilitate germination. Candidate transcription factors played important roles in GA3-promoted F. hupehensis seed germination, and Quantitative Real-time PCR (qRT-PCR) analysis verified the expression patterns of these genes. Exogenous GA3 increased the germination rate, vigor, and water absorption rate of F. hupehensis seeds. Our results provide novel insights into the transcriptional regulation mechanism of effect of exogenous GA3 on F. hupehensis seed germination. The transcriptome data generated in this study may be used for further molecular research on this unique species.

The Control of Seed Dormancy and Germination by Temperature, Light and Nitrate

Abstract: Seed dormancy and germination are two closely linked physiological traits that have great impacts on adaptation and survival of seed plants. Seed dormancy strengthen and germination potential are comprehensively influenced by a variety of internal factors and external environment cues. Environmental factors, such as water content, light condition, ambient temperature, and nitrogen availability, act as signal input to determine whether seeds keep in a dormant state or start to germinate. Light, temperature, and nitrogen availability are the most critical environmental factors that have profound impacts on seed dormancy and germination. However, the mechanisms underlying the regulation of seed dormancy and germination by environmental signals are still poorly understood. In this review, we summarize the current knowledge of signal transduction networks linking environmental stimulus to seed dormancy establishment, dormancy break and germination, underscoring the dominating roles of temperature, light, and nitric oxide. We review temperature, light, and nitric oxide signaling pathway separately as well as the integration of these signaling pathways with phytohormone abscisic acid (ABA) and gibberellins (GA) signaling pathway in the context of seed dormancy and germination.

Regulatory Mechanisms of bHLH Transcription Factors in Plant Adaptive Responses to Various Abiotic Stresses.

Abstract: Basic helix-loop-helix proteins (bHLHs) comprise one of the largest families of transcription factors in plants. They have been shown to be involved in responses to various abiotic stresses, such as drought, salinity, chilling, heavy metal toxicity, iron deficiency, and osmotic damages. By specifically binding to cis-elements in the promoter region of stress related genes, bHLHs can regulate their transcriptional expression, thereby regulating the plant's adaptive responses. This review focuses on the structural characteristics of bHLHs, the regulatory mechanism of how bHLHs are involved transcriptional activation, and the mechanism of how bHLHs regulate the transcription of target genes under various stresses. Finally, as increasing research demonstrates that flavonoids are usually induced under fluctuating environments, the latest research progress and future research prospects are described on the mechanisms of how flavonoid biosynthesis is regulated by bHLHs in the regulation of the plant's responses to abiotic stresses.

Purification of Tyrosine Hydroxylase from Callus Cultures of Portulaca grandiflora

Abstract: Tyrosine hydroxylase was separated from polyphenol oxidase activity and was highly purified from betacyanin producing callus cultures of Portulaca grandiflora. The purified enzyme catalyzed the formation of DOPA (L-3,4-dihydroxyphenylalanine) from tyrosine and required the pterin compounds (6-methyl-5,6,7,8-tetrahydropterin; 5,6,7,8-tetrahydrobiopterin; 6,7-dimethyl-5,6,7,8-tetrahydropterin) as coenzyme. The K(m) values for tyrosine and 6-methyl-5,6,7,8-tetrahydropterin were 0.5 mM and 0.15 mM, respectively. This enzyme was activated by Fe(2+) and Mn(2+), and inhibited by metal chelating agents.

Plant Volatile Organic Compounds Evolution: Transcriptional Regulation, Epigenetics and Polyploidy.

Abstract: Volatile organic compounds (VOCs) are emitted by plants as a consequence of their interaction with biotic and abiotic factors, and have a very important role in plant evolution. Floral VOCs are often involved in defense and pollinator attraction. These interactions often change rapidly over time, so a quick response to those changes is required. Epigenetic factors, such as DNA methylation and histone modification, which regulate both genes and transcription factors, might trigger adaptive responses to these evolutionary pressures as well as regulating the rhythmic emission of VOCs through circadian clock regulation. In addition, transgenerational epigenetic effects and whole genome polyploidy could modify the generation of VOCs' profiles of offspring, contributing to long-term evolutionary shifts. In this article, we review the available knowledge about the mechanisms that may act as epigenetic regulators of the main VOC biosynthetic pathways, and their importance in plant evolution.

Genome-wide identification and characterization of bHLH family genes from Ginkgo biloba.

Abstract: Basic helix-loop-helix (bHLH) proteins, one of the most important and largest transcription factor family in plants, play important roles in regulating growth and development, stress response. In recent years, many bHLH family genes have been identified and characterized in woody plants. However, a systematic analysis of the bHLH gene family has not been reported in Ginkgo biloba, the oldest relic plant species. In this study, we identifed a total of 85 GbbHLH genes from the genomic and transcriptomic databases of G. biloba, which were classified into 17 subfamilies based on the phylogenetic analysis. Gene structures analysis indicated that the number of exon-intron range in GbbHLHs from 0 to 12. The MEME analysis showed that two conserved motifs, motif 1 and motif 2, distributed in most GbbHLH protein. Subcellular localization analysis exhibited that most GbbHLHs located in nucleus and a few GbbHLHs were distributed in chloroplast, plasma membrane and peroxisome. Promoter cis-element analysis revealed that most of the GbbHLH genes contained abundant cis-elements that involved in plant growth and development, secondary metabolism biosynthesis, various abiotic stresses response. In addition, correlation analysis between gene expression and flavonoid content screened seven candidate GbbHLH genes involved in flavonoid biosynthesis, providing the targeted gene encoding transcript factor for increase the flavonoid production through genetic engineering in G. biloba.