Molecular genetical analysis of Plant gene expression by phytohormones

在缺水条件下，多种基因被诱导并被认为在胁迫耐受和反应中起作用。为了了解干旱胁迫对拟南芥的分子响应，我们从拟南芥中克隆了大约50个干旱诱导基因cdna。这些干旱诱导基因可分为两类，一类是参与抗旱的功能蛋白，另一类是参与胁迫反应的调节蛋白。我们分析了这些干旱诱导基因的表达模式，确定了初始脱水信号与基因表达之间至少有四条独立的信号转导途径。两个是aba依赖的，两个是aba独立的。我们发现了一个顺式作用元件（DRE，TACCGACAT），它参与了rd29A基因对脱水和冷应激的一个aba独立基因表达。利用酵母双杂交系统分离并分析了DRE结合蛋白的cdna （DREB）。他们被分为两类。它们编码更多的DNA结合蛋白，控制在AP2和EREBP蛋白中发现的保守的DNA结合基序。DREBl基因受低温诱导，DREB2基因受干旱和高盐诱导。这些结果表明，在低温和脱水条件下，DREB蛋白DREBl和DREB2作为转录因子分别在两条不同的信号转导通路中发挥作用。拟南芥干旱诱导基因rd22的诱导是由ABA介导的，但其ABA依赖性的表达需要蛋白质的生物合成，rd22启动子的一个67-bp区域是ABA应答性表达所必需的，并且包含几个DNA结合蛋白的保守基序，如MYC和MYB，但MYB，但没有ABREs。最近，用西南法以67-bp的DNA为探针克隆了一个转录因子MYC同源物的cDNA，这表明干旱诱导的MYC同源物可能在aba诱导的rd22表达中起作用。这些结果表明干旱或aba诱导的MYB和MYC转录因子在干旱胁迫下aba应答基因表达中起作用。少

Under water deficit conditions, various genes are induced and are thought to function in stress tolerance and response. To understand molecular responses to drougt stress, we cloned about 50 cDNAs for drought-inducib1e genes form Arabidopsis thaliana. These drought-inducible genes are classified into two groups, one is function proteins that are involved in drought tolerance and thc other is regulatory proteins involved in stress response. We analyzed the expression patterns of these drought-inducible genes, and identified at least four independent signal transduction pathways between the initial dehydration signal and gene expression. Two are ABA-dependentand two are ABA-independent.We identified a cis-acting elerment (DRE,TACCGACAT) involved in one of the ABA-independent gene expression of the rd29A gene in response to dehydration and cold stress. We isolated and analyzed cDNAs (DREB) for DRE binding proteins by yeast two hybrid system. They are classified in tow two subgroups.They e … More ncode DNA binding proteins that contoin a conserved DNA binding motif found in AP2 and EREBP proteins. DREBl genes are induced by low temperature, while DREB2 genes are induced by drought and high salinity. These results indicate that two DREB proteins, DREBl and DREB2, function as transcription factors in two separate signal transduction pathways under low temperature and dehydration, respectively.The induction of an Arabidopsis drought-inducible genes, rd22, is mediated by ABA,but requires protein biosynthesis for its ABA-dependent expression, A 67-bp region of the rd22 promoter is essential for its ABA-responsive expression, and contains several conserved motifs of DNA binding proteins, such as MYC and MYB,but MYB,but no ABREs. Rccently, a cDNA for a transcription factor MYC homologue was cloned by southwestern method using the 67-bp DNA as a probe, which suggests that drought-inducible MYC homologue may function in the ABA-inducible expression of rd22. These results indicates that drought-or ABA-inducible transcription factor(s) for MYB and MYC function in the ABA-responsive gene expression under drought stress. Less