Polyoxin N,a New Member of the Polyoxin Family

Eclosion hormone was purified 5,000-fold from the extracts of male adult heads of the silkworm, Bombyx mori. The fourteen-step purification procedure consisting of solvent extractions, fractional precipitations and chromatographies afforded a partially purified preparation of eclosion hormone, 1.8 μg of which showed activity in a Bombyx pharate adult. The hormone was inactivated by proteolytic enzymes. The molecular weight of eclosion hormone was estimated to be 8,400 ± 1,000 daltons by gel-filtration on Sephadex G-50.     

Co-expression analysis reveals a group of genes potentially involved in regulation of plant response to iron-deficiency

Iron (Fe) is an essential element for plant growth and development. Iron deficiency results in abnormal metabolisms from respiration to photosynthesis. Exploration of Fe-deficient responsive genes and their networks is critically important to understand molecular mechanisms leading to the plant adaptation to soil Fe-limitation. Co-expression genes are a cluster of genes that have a similar expression pattern to execute relatively biological functions at a stage of development or under a certain environmental condition. They may share a common regulatory mechanism. In this study, we investigated Fe-starved-related co-expression genes from Arabidopsis. From the biological process GO annotation of TAIR (The Arabidopsis Information Resource), 180 iron-deficient responsive genes were detected. Using ATTED-II database, we generated six gene co-expression networks. Among these, two modules of PYE and IRT1 were successfully constructed. There are 30 co-expression genes that are incorporated in the two modules (12 in PYE-module and 18 in IRT1-module). Sixteen of the co-expression genes were well characterized. The remaining genes (14) are poorly or not functionally identified with iron stress. Validation of the 14 genes using real-time PCR showed differential expression under iron-deficiency. Most of the co-expression genes (23/30) could be validated in pye and fit mutant plants with iron-deficiency. We further identified iron-responsive cis-elements upstream of the co-expression genes and found that 22 out of 30 genes contain the iron-responsive motif IDE1. Furthermore, some auxin and ethylene-responsive elements were detected in the promoters of the co-expression genes. These results suggest that some of the genes can be also involved in iron stress response through the phytohormone-responsive pathways.     

植物WRKY转录因子结构及功能研究进展

WRKY蛋白是植物所特有的转录因子家族.因WRKY结构域中的N-端均含有高度保守的WRJKYGQK氨基酸序列而得名.它能够与(T)TGACC(A/T)序列(W*box)发生特异性作用,调节启动子中含W-box元件的调节基因或功能基因的表达,从而参与植物的各种防卫反应,调节植物的发育和代谢等.近些年来.有关WRKY转录因子的研究很多,如模式生物中的拟南芥和水稻基因组中拥有大量的WRKY成员.主要介绍WRKY转录因子的结构特点及生物学功能.     

Roles of salicylic acid-responsive cis-acting elements and W-boxes in salicylic acid induction of VCH3 promoter in transgenic tobaccos

A salicylic acid (SA)-inducible VCH3 promoter was recently identified from grapevine (Vitisarnurensis) that contains two inverse SA-responsive cis-acting elements and four W-boxes.To furtherdemonstrate the roles of these elements,four fragments with lengths from-1187,-892,-589,-276 to 7 bp were fused with the β-glucuronidase (GUS) reporter géne and transferred to Nicotiana tobacum,together with another four VCH3 promoter fragments with mutation in the two inverse SA-responsiveelements.The functions,of each promoter fragment were-examined by analysis of GUS activity in thetransgenic tobacco root treated with SA.Enhanced GUS activity was shown in the roots of transgenictobaccos with the VCH3 (-1187)-GUS construct containing two SA-responsive cis-acting elements andfour W-boxes.However,GUS activity directed by the VCH3 (-892)-GUS construct,containing one SA cis-acting element and four W-boxes,was reduced by up to 35% compared with that in tobaccos transformedwith the VCH3 (-1187)-GUS construct,indicating that the SA cis-acting element plays an important role inSA induction of the VCH3 promoter.Neither the m2VCH3 (-1187)-GUS nor the mVCH3 (-892)-GUSconstruct,with mutation on the SA-responsive elements,abolished the expression of GUS activity,demon-strating that the W-boxes in the VCH3 promoter are also involved in SA induction.Histochemical arialysis ofGUS activity directed by each of the eight VCH3 promoter fragments showed that GUS was expressedspecifically in vascular tissue.It was concluded that both the SA-responsive cis-acting elements and the W-boxes are important for the SA induction of the VCH3 promoter.This promoter might have a potential usein plant genetic engineering.