Azevedo Cristina, Betsuyaku Shigeyuki, Peart Jack, Takahashi Akira, Noël Laurent, Sadanandom Ari, Casais Catarina, Parker Jane, Shirasu Ken
The Sainsbury Laboratory, John Innes Centre, Norwich, UK.
EMBO J. 2006 May 3;25(9):2007-16. doi: 10.1038/sj.emboj.7601084. Epub 2006 Apr 13.
A highly conserved eukaryotic protein SGT1 binds specifically to the molecular chaperone, HSP90. In plants, SGT1 positively regulates disease resistance conferred by many Resistance (R) proteins and developmental responses to the phytohormone, auxin. We show that silencing of SGT1 in Nicotiana benthamiana causes a reduction in steady-state levels of the R protein, Rx. These data support a role of SGT1 in R protein accumulation, possibly at the level of complex assembly. In Arabidopsis, two SGT1 proteins, AtSGT1a and AtSGT1b, are functionally redundant early in development. AtSGT1a and AtSGT1b are induced in leaves upon infection and either protein can function in resistance once a certain level is attained, depending on the R protein tested. In unchallenged tissues, steady-state AtSGT1b levels are at least four times greater than AtSGT1a. While the respective tetratricopeptide repeat (TPR) domains of SGT1a and SGT1b control protein accumulation, they are dispensable for intrinsic functions of SGT1 in resistance and auxin responses.
一种高度保守的真核蛋白SGT1能特异性结合分子伴侣HSP90。在植物中，SGT1正向调控许多抗性（R）蛋白赋予的抗病性以及对植物激素生长素的发育响应。我们发现，沉默本氏烟草中的SGT1会导致R蛋白Rx的稳态水平降低。这些数据支持SGT1在R蛋白积累中发挥作用，可能是在复合物组装水平。在拟南芥中，两种SGT1蛋白AtSGT1a和AtSGT1b在发育早期功能冗余。AtSGT1a和AtSGT1b在感染后叶片中被诱导表达，一旦达到一定水平，任一蛋白都能在抗病中发挥作用，这取决于所测试的R蛋白。在未受挑战的组织中，AtSGT1b的稳态水平至少是AtSGT1a的四倍。虽然SGT1a和SGT1b各自的四肽重复（TPR）结构域控制蛋白积累，但它们对于SGT1在抗病性和生长素响应中的内在功能是可有可无的。
