Genomics of Plant Stress laboratory, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2780-157, Oeiras, Portugal.
Plant Mol Biol. 2013 Nov;83(4-5):351-63. doi: 10.1007/s11103-013-0092-6. Epub 2013 Jun 19.
Plants can cope with adverse environmental conditions through the activation of stress response signalling pathways, in which the proteasome seems to play an important role. However, the mechanisms underlying the proteasome-mediated stress response in rice are still not fully understood. To address this issue, we have identified a rice E3-ubiquitin ligase, OsHOS1, and characterized its role in the modulation of the cold stress response. Using a RNA interference (RNAi) transgenic approach we found that, under cold conditions, the RNAi::OsHOS1 plants showed a higher expression level of OsDREB1A. This was correlated with an increased amount of OsICE1, a master transcription factor of the cold stress signalling. However, the up-regulation of OsDREB1A was transient and the transgenic plants did not show increased cold tolerance. Nevertheless, we could confirm the interaction of OsHOS1 with OsICE1 by Yeast-Two hybrid and bi-molecular fluorescence complementation in Arabidopsis protoplasts. Moreover, we could also determine through an in vitro degradation assay that the higher amount of OsICE1 in the transgenic plants was correlated with a lower amount of OsHOS1. Hence, we could confirm the involvement of the proteasome in this response mechanism. Taken together our results confirm the importance of OsHOS1, and thus of the proteasome, in the modulation of the cold stress signalling in rice.
植物可以通过激活应激反应信号通路来应对不利的环境条件，其中蛋白酶体似乎起着重要作用。然而，水稻中蛋白酶体介导的应激反应的机制仍不完全清楚。为了解决这个问题，我们鉴定了一个水稻 E3-泛素连接酶 OsHOS1，并对其在调节冷胁迫反应中的作用进行了表征。通过 RNA 干扰（RNAi）转基因方法，我们发现，在低温条件下，RNAi::OsHOS1 植株表现出更高水平的 OsDREB1A。这与 OsICE1 的含量增加有关，OsICE1 是冷胁迫信号的主要转录因子。然而，OsDREB1A 的上调是短暂的，转基因植物并没有表现出增强的耐寒性。然而，我们可以通过酵母双杂交和拟南芥原生质体中的双分子荧光互补实验证实 OsHOS1 与 OsICE1 的相互作用。此外，我们还可以通过体外降解实验确定，转基因植物中 OsICE1 的含量较高与 OsHOS1 的含量较低有关。因此，我们可以确认蛋白酶体参与了这一反应机制。总之，我们的研究结果证实了 OsHOS1 及其蛋白酶体在调节水稻冷胁迫信号中的重要性。
