Jacobsen S E, Binkowski K A, Olszewski N E
Department of Plant Biology, University of Minnesota, St. Paul 55108, USA.
Proc Natl Acad Sci U S A. 1996 Aug 20;93(17):9292-6. doi: 10.1073/pnas.93.17.9292.
Gibberellins (GAs) are a major class of plant hormones that control many developmental processes, including seed development and germination, flower and fruit development, and flowering time. Genetic studies with Arabidopsis thaliana have identified two genes involved in GA perception or signal transduction. A semidominant mutation at the GIBBERELLIN INSENSITIVE (GAI) locus results in plants resembling GA-deficient mutants but exhibiting reduced sensitivity to GA. Recessive mutations at the SPINDLY (SPY) locus cause a phenotype that is consistent with constitutive activation of GA signal transduction. Here we show that a strong allele of spy is completely epistatic to gai, indicating that SPY acts downstream of GAI. We have cloned the SPY gene and shown that it encodes a new type of signal transduction protein, which contains a tetratricopeptide repeat region, likely serving as a protein interaction domain, and a novel C-terminal region. Mutations in both domains increase GA signal transduction. The presence of a similar gene in Caenorhabditis elegans suggests that SPY represents a class of signal transduction proteins that is present throughout the eukaryotes.
赤霉素（GAs）是一类主要的植物激素，可调控许多发育过程，包括种子发育与萌发、花和果实发育以及开花时间。对拟南芥的遗传学研究已鉴定出两个参与赤霉素感知或信号转导的基因。赤霉素不敏感（GAI）位点的一个半显性突变导致植株类似于赤霉素缺陷型突变体，但对赤霉素的敏感性降低。细长（SPY）位点的隐性突变导致一种与赤霉素信号转导组成型激活相一致的表型。在此我们表明，spy的一个强等位基因对gai完全上位，表明SPY在GAI下游起作用。我们已克隆了SPY基因，并表明它编码一种新型信号转导蛋白，该蛋白含有一个四肽重复区域，可能作为蛋白质相互作用结构域，以及一个新的C末端区域。两个结构域中的突变均增加赤霉素信号转导。秀丽隐杆线虫中存在类似基因表明，SPY代表一类在整个真核生物中都存在的信号转导蛋白。
