Tseng T S, Swain S M, Olszewski N E
Department of Plant Biology and Plant Molecular Genetics Institute, University of Minnesota, St. Paul, Minnesota 55108, USA.
Plant Physiol. 2001 Jul;126(3):1250-8. doi: 10.1104/pp.126.3.1250.
The SPINDLY (SPY) protein of Arabidopsis is a negative regulator of gibberellin (GA) response. The SPY protein has 10 copies of the tetratricopeptide repeat (TPR) at the N terminus. TPR motifs function as protein-protein interaction domains. Several spy alleles are affected only in the TPR region suggesting that protein-protein interactions mediated by this domain are important for proper GA signaling. We have used a reverse genetics approach to further investigate the role of the TPR domain. The TPR domain of SPY was overexpressed in wild-type, gai, and spy plants. Expression of the TPR domain alone is not sufficient to rescue spy mutants. Expression of the TPR domain in a wild-type background produces phenotypes similar to those caused by loss-of-function spy mutants including resistance to GA biosynthesis inhibitors, short hypocotyl length, and early flowering. The dwarfing of the floral shoot internodes caused by the gai mutation was suppressed by expression of the TRP domain. Expression of the TPR domain had no effect on the abundance of endogenous SPY mRNA. The TPR domain was found to interact with SPY both in vitro and in yeast two-hybrid assays. These data indicate that the TPR domain of SPY can participate in protein-protein interactions and that these interactions are important for the proper functioning of SPY.
拟南芥的SPINDLY（SPY）蛋白是赤霉素（GA）反应的负调控因子。SPY蛋白在N端有10个四肽重复序列（TPR）拷贝。TPR基序作为蛋白质-蛋白质相互作用结构域发挥作用。几个spy等位基因仅在TPR区域受到影响，这表明该结构域介导的蛋白质-蛋白质相互作用对于正常的GA信号传导很重要。我们采用反向遗传学方法进一步研究TPR结构域的作用。SPY的TPR结构域在野生型、gai和spy植物中过表达。单独TPR结构域的表达不足以拯救spy突变体。在野生型背景中TPR结构域的表达产生的表型类似于功能缺失的spy突变体所导致的表型，包括对GA生物合成抑制剂的抗性、下胚轴长度缩短和早花。由gai突变引起的花茎节间矮化被TRP结构域的表达所抑制。TPR结构域的表达对内源SPY mRNA的丰度没有影响。在体外和酵母双杂交试验中发现TPR结构域与SPY相互作用。这些数据表明SPY的TPR结构域可以参与蛋白质-蛋白质相互作用，并且这些相互作用对于SPY的正常功能很重要。
