Plants show distinct morphologies in different light conditions through a process called photomorphogenesis. A predominant feature of photomorphogenesis is the reduced growth of seedlings under light conditions compared with darkness. For this adaptive event, the most well-known molecular mechanism involves photoreceptor-mediated inhibition of cell elongation. However, it is not known whether additional pathways exist. Here, we describe a newly discovered pathway of light-modulated plant growth mediated by the halotolerance protein HAL3, a flavin mononucleotide (FMN)-binding protein involved in cell division. We found that light, especially blue light, suppresses growth of rice seedlings by reducing the activity of Oryza sativa (Os) HAL3. Both in vitro and in vivo studies showed that OsHAL3 is structurally inactivated by light through photo-oxidation and by direct interaction with photons. In addition, the transcriptional expression of OsHAL3 is synergistically regulated by different light conditions. Further investigation suggested that OsHAL3 promotes cell division by recruiting a ubiquitin system, rather than by its 4'-phosphopantothenoylcysteine (PPC) decarboxylase activity. Our results uncover a new mechanism for light-regulated plant growth, namely, light not only inhibits cell elongation but also suppresses cell division through HAL3 and E3 ubiquitin ligase. This study thus brings new insights into our understanding of plant photomorphogenesis.
植物在不同的光條件下具有不同的形態(tài)，這一過程稱為光形態(tài)建成。與在暗下相比，植物在光下生長受到抑制，這是光形態(tài)建成的一個(gè)顯著特征。在光形態(tài)建成中了解最為清楚的分子機(jī)制是光受體介導(dǎo)的光抑制細(xì)胞伸長。然而是否還存在其他的通路還并不清楚。本文我們發(fā)現(xiàn)了一個(gè)由耐鹽蛋白HAL3介導(dǎo)的光調(diào)控植物生長的新通路。HAL3是一個(gè)黃素單核苷酸(FMN)結(jié)合蛋白，參與細(xì)胞的分裂。我們發(fā)現(xiàn)陽光尤其是藍(lán)光可以降低OsHAL3的活性從而抑制水稻幼苗的生長。另外OsHAL3的表達(dá)還受不同光照條件的調(diào)節(jié)。進(jìn)一步研究表明OsHAL3通過招募泛素蛋白降解系統(tǒng)來促進(jìn)細(xì)胞的分裂，而不是依賴于其4'-磷酸泛酰半胱氨酸脫羧酶(PPC)的活性。我們的結(jié)果揭示了光調(diào)控植物生長的新機(jī)制，即光不僅抑制細(xì)胞的伸長同時(shí)還通過HAL3和E3泛素連接酶抑制細(xì)胞的分裂。因此本研究加深了我們對(duì)植物光形態(tài)建成的認(rèn)識(shí)。