Action of Le and Lip1 Genes in Controlling Stem Growth of Pisum by Gibberellins and Light

该研究将利用豌豆的赤霉素（GA）生物合成突变体和光生突变体来研究植物调节活性激素水平和靶组织反应性的机制。在豌豆矮秆突变体中，完整植株中3β -羟基化作用导致赤霉素A20向GA1的转化减少。GA1是豌豆节间生长的活性基因。最近报道的一些结果需要重新检查le突变的生化基础。对标记的GAs进行体内和体外饲养研究将用于检查le突变是否干扰GA20从叶片（这是其推定的合成位点）到茎的运输，或者le位点是否可以编码调节因子。GA代谢物的定性和定量分析将使用气相色谱-质谱法进行，以提供明确的鉴定。由于3β -羟基化是GA生物合成中最重要的步骤之一，因此必须确定le突变的功能基础。新发现的豌豆lip1突变导致不依赖于光的光形态发生。在这个突变体中，通常发生在豌豆幼苗从黑暗转到光明（去黄化）时的茎生长严重减少，在完全黑暗中表现出来。生化研究表明光敏色素A的信号转导途径在突变体中受到影响。为了确定GA生物化学的哪些方面是光生的一个因素，将对这种GA水平、代谢和组织反应性突变的影响进行调查。＊＊＊

9318358 Sponsel The proposed research will utilize gibberellin (GA) biosynthetic mutants and photomophogenetic mutants of Pisum sativum (garden pea) to investigate the mechanisms by which a plant can regulate both the levels of active hormone and the responsiveness of its target tissue. In the le dwarf mutant of pea the conversion of gibberellin A20 to GA1 by 3Beta-hydroxylation is reduced in intact plants. GA1 is the active GA for internode growth in pea. Some recently reported results necessitate a re-examination of the biochemical basis for the le mutation. In vivo and in vitro feeding studies of labeled GAs will be used to examine whether the le mutation interferes with the transport of GA20 from leaves (which are its putative site of synthesis) to stems, or whether the le locus could code for a regulatory factor. Qualitative and quantitative analyses of the GA metabolites will be conducted using gas chromatography-mass spectrometry providing definitive identification. Since 3Beta- hydroxylation is one of the most important steps in GA biosynthesis it is imperative that the functional basis of the le mutation is defined. The newly characterized lip1 mutation of pea results in light independent photomorphogenesis. In this mutant the severe reduction in stem growth which normally takes place when pea seedlings are transferred from dark to light (de-etiolation) is manifest in complete darkness. Biochemical studies suggest that the signal transduction pathway from phytochrome A is affected in the mutant. An investigation of the effect of this mutation of GA levels, metabolism and on tissue responsiveness will be conducted in order to define which aspects of GA biochemistry are a factor in photomophogenesis. ***