The BEL1-like transcription factor GhBLH5-A05 participates in cotton response to drought stress

Drought stress impairs crop growth and development.BEL1-like family transcription factors may be involved in plant response to drought stress,but little is known of the molecular mechanism by which these proteins regulate plant response and defense to drought stress.Here we show that the BEL1-like transcription factor GhBLH5-A05 functions in cotton(Gossypium hirsutum)response and defense to drought stress.Expression of GhBLH5-A05 in cotton was induced by drought stress.Overexpression of GhBLH5-A05 in both Arabidopsis and cotton increased drought tolerance,whereas silencing GhBLH5-A05 in cotton resulted in elevated sensitivity to drought stress.GhBLH5-A05 binds to cis elements in the promoters of GhRD20-A09 and GhDREB2C-D05 to activate the expression of these genes.GhBLH5-A05 interacted with the KNOX transcription factor GhKNAT6-A03.Co-expression of GhBLH5-A05 and GhKNAT6-A03 increased the transcription of GhRD20-A09 and GhDREB2C-D05.We conclude that GhBLH5-A05 acts as a regulatory factor with GhKNAT6-A03 functioning in cotton response to drought stress by activating the expression of the drought-responsive genes GhRD20-A09 and GhDREB2C-D05.

棉纤维发育优势表达及伸长必需的基因GhACT1

Each fiber of cotton (Gossypium hirsutum) is a single epidermal cell that rapidly elongates to 2.5 ～3.0 cm from ovule surface within about 16days after anthesis. A large number of genes are required for fiber differentiation and development, but it is unknown how these genes control and regulate the process of fiber development. ……

Expression of a cotton MADS-box gene is regulated in anther development and in response to phytohormone signaling

MADS-box gene family encodes a large number and variety of transcription regulators in plants. In this study, a cDNA, GhMADS9, encoding a typical MADS protein with 230 amino acids was isolated from cotton flower cDNA library. Subsequently, a 1,623 bp genomic DNA fragment of GhMADS9 gene was isolated in cotton by PCR. Compared with its cDNA sequence, six introns were found in GhMADS9 gene. Fluorescent microscopy indicated that GhMADS9 protein localized in the nucleus. Transactivation activity assay in yeast cells revealed that GhMADS9 protein did not show transcriptional activation. Quantitative RT-PCR analysis showed that GhMADS9 was specially expressed in cotton anthers. Further in situ hybridization analysis demonstrated that strong expression of GhMADS9 gene was detected in developing pollens, but no or weak signals were found in the other anther tissues. Furthermore, GhMADS9 expression was dramatically up-regulated in anthers with abscisic acid (ABA) treatment, whereas its activity was down-regulated when treated by gibberellin (GA3). Collectively, our results suggest that GhMADS9 is a transcription factor and might be involved in cotton anther/pollen development and in response to ABA and GA3 signaling.

Cotton AnnGh3 Encoding an Annexin Protein is Preferentially Expressed in Fibers and Promotes Initiation and Elongation of Leaf Trichomes in Transgenic Arabidopsis

The annexins are a multifamily of calcium-regulated phospholipid-binding proteins. To investigate the roles of annexins in fiber development, four genes encoding putative annexin proteins were isolated from cotton （Gossypium hirsutum） and designated AnnGh3, AnnGh4, AnnGh5, and AnnGh6. Quantitative reverse transcription-polymerase chain reaction （qRT-PCR） results indicated that AnnGh3, AnnGh4, and AnnGh5 were preferentially expressed in fibers, while the transcripts of AnnGh6 were predominantly accumulated in roots. During fiber development, the transcripts of AnnGh3/4/5 genes were mainly accumulated in rapidly elongating fibers. With fiber cells further developed, their expression activity was dramatically declined to a relatively low level. In situ hybridization results indicated that AnnGh3 and AnnGh5were expressed in initiating fiber cells （0-2 DPA）. Additionally, their expression in fibers was also regulated by phytohormones and [Ca2~]. Subcellular localization analysis discovered that AnnGh3 protein was localized in the cytoplasm. Overexpression of AnnGh3 in Arabidopsis resulted in a significant increase in trichome density and length on leaves of the transgenic plants, suggesting that AnnGh3 may be involved in fiber cell initiation and elongation of cotton.

GhKNL1 controls fiber elongation and secondary cell wall synthesis by repressing its downstream genes in cotton(Gossypium hirsutum)

Cotton which produces natural fiber materials for the textile industry is one of the most important crops in the world. Class II KNOX proteins are often considered as transcription factors in regulating plant secondary cell wall(SCW) formation. However,the molecular mechanism of the KNOX transcription factor-regulated SCW synthesis in plants(especially in cotton) remains unclear in details so far. In this study, we show a cotton class II KNOX protein(Gh KNL1) as a transcription repressor functioning in fiber development. The Gh KNL1-silenced transgeniccotton produced longer fibers with thicker SCWs,whereas Gh KNL1 dominant repression transgenic lines displayed the opposite fiber phenotype, compared with controls. Further experiments revealed that Gh KNL1 could directly bind to promoters of Gh Ces A4-2/4-4/8-2 and Gh MYB46 for modulating cellulose synthesis during fiber SCW development in cotton. On the other hand, Gh KNL1 could also suppress expressions of Gh EXPA2 D/4 A-1/4 D-1/13 A through binding to their promoters for regulating fiber elongation of cotton. Taken together, these data revealed Gh KNL1 functions in fiber elongation and SCW formation by directly repressing expressions of its target genes related to cell elongation and cellulose synthesis. Thus, our data provide an effective clue for potentially improving fiber quality by genetic manipulation of Gh KNL1 in cotton breeding.