DataSheet_1_SUMOylation of OsPSTOL1 is essential for regulating phosphate starvation responses in rice and Arabidopsis.pdf

Although rice is one of the main sources of calories for most of the world, nearly 60% of rice is grown in soils that are low in phosphorus especially in Asia and Africa. Given the limitations of bioavailable inorganic phosphate (Pi) in soils, it is important to develop crops tolerant to low phosphate in order to boost food security. Due to the immobile nature of Pi, plants have developed complex molecular signalling pathways that allow them to discern changes in Pi concentrations in the environment and adapt their growth and development. Recently, in rice, it was shown that a specific serine–threonine kinase known as Phosphorus-starvation tolerance 1 (PSTOL1) is important for conferring low phosphate tolerance in rice. Nonetheless, knowledge about the mechanism underpinning PSTOL1 activity in conferring low Pi tolerance is very limited in rice. Post-translation modifications (PTMs) play an important role in plants in providing a conduit to detect changes in the environment and influence molecular signalling pathways to adapt growth and development. In recent years, the PTM SUMOylation has been shown to be critical for plant growth and development. It is known that plants experience hyperSUMOylation of target proteins during phosphate starvation. Here, we demonstrate that PSTOL1 is SUMOylated in planta, and this affects its phosphorylation activity. Furthermore, we also provide new evidence for the role of SUMOylation in regulating PSTOL1 activity in plant responses to Pi starvation in rice and Arabidopsis. Our data indicated that overexpression of the non-SUMOylatable version of OsPSTOL1 negatively impacts total root length and total root surface area of rice grown under low Pi. Interestingly, our data also showed that overexpression of OsPSTOL1 in a non-cereal species, Arabidopsis, also positively impacts overall plant growth under low Pi by modulating root development. Taken together our data provide new evidence for the role of PSTOL1 SUMOylation in mediating enhanced root development for tolerating phosphate-limiting conditions.

尽管水稻是全球绝大多数人口的主要热量来源之一，但全球近60%的水稻种植于磷素匮乏的土壤中，这一情况在亚洲与非洲尤为突出。鉴于土壤中生物可利用无机磷酸盐（bioavailable inorganic phosphate, Pi）的供给有限，培育耐低磷作物对于保障粮食安全至关重要。由于Pi在土壤中移动性极差，植物演化出了复杂的分子信号通路，使其能够感知环境中Pi浓度的变化，并据此调整自身的生长与发育进程。近期研究表明，水稻中一种名为磷饥饿耐受1（Phosphorus-starvation tolerance 1, PSTOL1）的特异性丝氨酸-苏氨酸激酶（serine–threonine kinase），在赋予水稻耐低磷特性的过程中发挥关键作用。然而，目前学界对水稻中PSTOL1介导低Pi耐受性的作用机制仍知之甚少。翻译后修饰（Post-translation modifications, PTMs）是植物感知环境变化、调控分子信号通路以适配生长发育需求的重要途径。近年来的研究证实，类泛素化修饰（SUMOylation）这种翻译后修饰方式对植物的生长与发育至关重要。已有研究证实，植物在磷饥饿胁迫下，其靶蛋白会发生过度类泛素化修饰。本研究证实，PSTOL1可在植物体内（in planta）发生类泛素化修饰，且该修饰会影响其磷酸化激酶活性。此外，本研究还为类泛素化修饰在水稻与拟南芥（Arabidopsis）中调控PSTOL1活性、进而参与植物应对Pi饥饿胁迫的过程提供了全新的实验证据。本研究数据显示，在低Pi培养条件下，过表达无法发生类泛素化修饰的OsPSTOL1，会对水稻的总根长与总根表面积产生显著负面影响。值得注意的是，本研究数据同时证实，在非谷类植物拟南芥中过表达OsPSTOL1，同样可通过调控根系发育，在低Pi条件下促进植株整体生长。综上，本研究数据为PSTOL1的类泛素化修饰介导根系发育增强、进而帮助植物耐受磷素限制环境的作用机制提供了全新的实验依据。