Mao Xingxue, Zhang Jianjun, Liu Wuge, Yan Shijuan, Liu Qing, Fu Hua, Zhao Junliang, Huang Wenjie, Dong Jingfang, Zhang Shaohong, Yang Tifeng, Yang Wu, Liu Bin, Wang Feng
Guangdong Academy of Agricultural Sciences, Rice Research Institute, Guangzhou, 510640, China.
Guangdong Key Laboratory of New Technology in Rice Breeding, Guangzhou, 510640, China.
Rice (N Y). 2019 Jan 22;12(1):2. doi: 10.1186/s12284-018-0260-z.
Seed dormancy directly affects the phenotype of pre-harvest sprouting, and ultimately affects the quality and yield of rice seeds. Although many genes controlling seed dormancy have been cloned from cereals, the regulatory mechanisms controlling this process are complex, and much remains unknown. The MAPK cascade is involved in many signal transduction pathways. Recently, MKK3 has been reported to be involved in the regulation of seed dormancy, but its mechanism of action is unclear.
We found that MKKK62-overexpressing rice lines (OE) lost seed dormancy. Further analyses showed that the abscisic acid (ABA) sensitivity of OE lines was decreased. In yeast two-hybrid experiments, MKKK62 interacted with MKK3, and MKK3 interacted with MAPK7 and MAPK14. Knock-out experiments confirmed that MKK3, MAPK7, and MAPK14 were involved in the regulation of seed dormancy. The OE lines showed decreased transcript levels of OsMFT, a homolog of a gene that controls seed dormancy in wheat. The up-regulation of OsMFT in MKK3-knockout lines (OE/mkk3) and MAPK7/14-knockout lines (OE/mapk7/mapk14) indicated that the MKKK62-MKK3-MAPK7/MAPK14 system controlled seed dormancy by regulating the transcription of OsMFT.
Our results showed that MKKK62 negatively controls seed dormancy in rice, and that during the germination stage and the late stage of seed maturation, ABA sensitivity and OsMFT transcription are negatively controlled by MKKK62. Our results have clarified the entire MAPK cascade controlling seed dormancy in rice. Together, these results indicate that protein modification by phosphorylation plays a key role in controlling seed dormancy.
种子休眠直接影响收获前发芽的表型，并最终影响水稻种子的品质和产量。尽管已经从谷类作物中克隆出许多控制种子休眠的基因，但控制这一过程的调控机制很复杂，仍有许多未知之处。促分裂原活化蛋白激酶（MAPK）级联参与许多信号转导途径。最近，有报道称MKK3参与种子休眠的调控，但其作用机制尚不清楚。
我们发现过表达MKKK62的水稻株系（OE）失去了种子休眠。进一步分析表明，OE株系对脱落酸（ABA）的敏感性降低。在酵母双杂交实验中，MKKK62与MKK3相互作用，MKK3与MAPK7和MAPK14相互作用。基因敲除实验证实，MKK3、MAPK7和MAPK14参与种子休眠的调控。OE株系中控制种子休眠的小麦同源基因OsMFT的转录水平降低。在MKK3基因敲除株系（OE/mkk3）和MAPK7/14基因敲除株系（OE/mapk7/mapk14）中OsMFT的上调表明，MKKK62-MKK3-MAPK7/MAPK14系统通过调节OsMFT的转录来控制种子休眠。
我们的结果表明，MKKK62负调控水稻种子休眠，并且在种子萌发期和种子成熟后期，ABA敏感性和OsMFT转录受到MKKK62的负调控。我们的结果阐明了控制水稻种子休眠的整个MAPK级联。总之，这些结果表明磷酸化的蛋白质修饰在控制种子休眠中起关键作用。
