Post embryonic growth of plants depends on cell division activity in the shoot and root meristems, in conjunction with subsequent cell differentiation. Under environmental stress conditions, where plant growth is moderately impaired, the meristematic activity is maintained by mechanisms as yet unknown. We previously showed that the rice protein RSS1, whose stability is regulated depending on the cell cycle phases, is a key factor for the maintenance of meristematic activity under stressful conditions. RSS1 interacts with a catalytic subunit of protein phosphatase 1 (PP1), but other molecular characteristics are largely unknown. Here we show that RSS1 interacts with all the PP1 expressed in the shoot apex of rice. This interaction requires one of the conserved regions of RSS1, which is important for RSS1 function. Interestingly, the recombinant RSS1 protein is highly resistant to heat with respect to its anti-coagulability and binding activity to PP1. The features of RSS1 are reminiscent of those of inhibitor-2 of animals, although it is likely that the mode of function of RSS1 is different from that of inhibitor-2. Noticeably, RSS1 binds to PP1 under extremely high ionic strength conditions in vitro. Therefore, RSS1 possibly functions by forming a stable complex with PP1.
植物胚后發(fā)育依賴于莖端和根端分生組織的細(xì)胞分裂以及隨后的細(xì)胞分化。在環(huán)境脅迫條件下，植物的生長(zhǎng)被部分破壞，而分生組織仍維持有活性，但其中的機(jī)制尚不清楚。我們之前發(fā)現(xiàn)水稻RSS1蛋白的穩(wěn)定性受細(xì)胞周期階段的調(diào)節(jié)，RSS1是維持脅迫條件下分生活性的一個(gè)重要因子。RSS1與蛋白磷酸酶PP1 的一個(gè)催化亞基互作，但是關(guān)于RSS1的其他分子特征還不清楚。這里我們發(fā)現(xiàn)RSS1與水稻莖頂端表達(dá)的所有PP1互作。這一互作需要RSS1中一個(gè)對(duì)功能非常重要的保守區(qū)域。有意思的是RSS1重組蛋白的抗凝血以及PP1結(jié)合活性高度耐熱。RSS1的這些特征與動(dòng)物inhibitor-2類似，雖然RSS1的作用模式與inhibitor-2不同。值得注意的是在體外RSS1在極高離子強(qiáng)度下與PP1結(jié)合。因此，RSS1可能與PP1形成穩(wěn)定的復(fù)合物發(fā)揮功能。