Zhang Xiang, Long Yan, Huang Jingjing, Xia Jixing
State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, Nanning, 530004, China.
Rice (N Y). 2020 Dec 7;13(1):79. doi: 10.1186/s12284-020-00440-1.
Salt stress threatens crop yields all over the world. Many NAC transcription factors have been reported to be involved in different abiotic stress responses, but it remains unclear how loss of these transcription factors alters the transcriptomes of plants. Previous reports have demonstrated that overexpression of OsNAC45 enhances salt and drought tolerance in rice, and that OsNAC45 may regulate the expression of two specific genes, OsPM1 and OsLEA3-1.
Here, we found that ABA repressed, and NaCl promoted, the expression of OsNAC45 in roots. Immunostaining showed that OsNAC45 was localized in all root cells and was mainly expressed in the stele. Loss of OsNAC45 decreased the sensitivity of rice plants to ABA and over-expressing this gene had the opposite effect, which demonstrated that OsNAC45 played an important role during ABA signal responses. Knockout of OsNAC45 also resulted in more ROS accumulation in roots and increased sensitivity of rice to salt stress. Transcriptome sequencing assay found that thousands of genes were differently expressed in OsNAC45-knockout plants. Most of the down-regulated genes participated in plant stress responses. Quantitative real time RT-PCR suggested that seven genes may be regulated by OsNAC45 including OsCYP89G1, OsDREB1F, OsEREBP2, OsERF104, OsPM1, OsSAMDC2, and OsSIK1.
These results indicate that OsNAC45 plays vital roles in ABA signal responses and salt tolerance in rice. Further characterization of this gene may help us understand ABA signal pathway and breed rice plants that are more tolerant to salt stress.
盐胁迫威胁着全球农作物产量。许多NAC转录因子已被报道参与不同的非生物胁迫反应，但这些转录因子的缺失如何改变植物转录组仍不清楚。先前的报道表明，OsNAC45的过表达增强了水稻的耐盐性和耐旱性，并且OsNAC45可能调控两个特定基因OsPM1和OsLEA3-1的表达。
在此，我们发现脱落酸（ABA）抑制而氯化钠（NaCl）促进OsNAC45在根部的表达。免疫染色显示OsNAC45定位于所有根细胞中，且主要在中柱表达。OsNAC45的缺失降低了水稻植株对ABA的敏感性，而过表达该基因则产生相反的效果，这表明OsNAC45在ABA信号反应中起重要作用。敲除OsNAC45还导致根部更多活性氧（ROS）积累，并增加了水稻对盐胁迫的敏感性。转录组测序分析发现，在OsNAC45敲除植株中有数千个基因表达存在差异。大多数下调基因参与植物胁迫反应。实时定量逆转录聚合酶链反应（qRT-PCR）表明，七个基因可能受OsNAC45调控，包括OsCYP89G1、OsDREB1F、OsEREBP2、OsERF104、OsPM1、OsSAMDC2和OsSIK1。
这些结果表明OsNAC45在水稻ABA信号反应和耐盐性中起关键作用。对该基因的进一步表征可能有助于我们了解ABA信号通路，并培育出更耐盐胁迫的水稻品种。
