The diverse functions of phosphoenolpyruvate carboxylase(PEPCase;EC 4.1.1.31) in C3 plants are not as well understood as in C4 plants.To investigate the functions of PEPCase in C3 plants,rapeseed(Brassica napus L.) PEPCase gene(referred to as BNPE15) was silenced by the RNA interference(RNAi) technique.Under normal growth conditions,no significant difference in lipid content and fatty acid composition were found between wild-type(WT) and transgenic rapeseed plants.However,when these plants were subjected to osmotic stress induced by osmoticum polyethylene glycol(PEG-6000),membrane permeability and membrane lipid peroxidization in roots and leaves of transgenic plants were higher than those of WT plants.It suggested that transgenic plants are more susceptible to osmotic stress than WT plants.Taken together,the results showed that the suppression of PEPCase by RNAi leads to susceptibility to osmotic stress in rapeseed,and PEPCase is involved in the response of C3 plants to environmental stress.
Mei ChenYunlai TangJingmei ZhangMingfeng YangYinong Xu
Two cDNAs encoding putative type 1 acyl-CoA: diacylglycerol acyltransferases (DGAT1, EC 2.3.1.20), were cloned from Tetraena mongolica Maxim., an extreme xerophyte with high oil content in the stems. The 1,488-bp and 1,485-bp of the open reading frame (ORF) of the two cDNAs, designated as TmDGAT1a and TmDGAT1b, were both predicted to encode proteins of 495 and 494 amino acids, respectively. Southern blot analysis revealed that TmDGAT1a and TmDGAT1b both had low copy numbers in the T. mongolica genome. In addition to ubiquitous expression with different intensity in different tissues, including stems, leaves and roots, TmDGAT1a and TmDGAT1b, were found to be strongly induced by high salinity, drought and osmotic stress, resulting in a remarkable increase of triacylglycerol (TAG) accumulation in T. mongolica plantlets. TmDGAT1a and TmDGAT1b activities were confirmed in the yeast H1246 quadruple mutant (DGA1, LRO1, ARE1, ARE2) by restoring DGAT activity of the mutant host to produce TAG. Overexpression of TmDGAT1a and TmDGAT1b in soybean hairy roots as well as in T. mongolica calli both resulted in an increase in oil content (ranging from 37% to 108%), accompanied by altered fatty acid profiles.
AP2/EREBP家族的转录因子在调控植物生长发育和应答环境胁迫方面具有重要作用。利用同源克隆结合RACE(rapid-amplification of cDNA ends)技术,从四合木(Tetraena mongolica)中克隆了AP2/EREBP家族的基因,将其命名为TmAP2-1(GenBank登录号:JQ676996)。序列分析结果表明,该基因的开放阅读框长度为1452bp,编码483个氨基酸;比对结果显示TmAP2-1有2个AP2/ERF结构域,属于AP2/EREBP转录因子家族的AP2亚家族。亚细胞定位实验结果表明,TmAP2-1定位在细胞核中。该基因编码的蛋白在酵母中没有转录激活活性。利用Real-timePCR检测发现该基因在根、茎、叶等器官中均表达,且在叶中表达量最高。此外,TmAP2-1还受到NaCl、低温、PEG和ABA的强烈诱导,推测TmAP2-1可能参与四合木的逆境胁迫响应。在四合木愈伤组织中过表达该基因能够降低四合木愈伤组织中油脂的含量,同时提高可溶性糖的含量,暗示该基因可能通过影响糖代谢过程参与逆境胁迫响应。
