Huang Menghan, Liu Yang, Bian Qianwen, Zhao Wenjing, Zhao Juan, Liu Qingpo
The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, College of Advanced Agricultural Sciences, Zhejiang A&F University, Lin'an, Hangzhou, 311300, P. R. China.
Plant J. 2024 Dec;120(6):2485-2499. doi: 10.1111/tpj.17124. Epub 2024 Nov 7.
Arsenic (As) is extremely toxic to plants, posing a serious concern for food safety. Identification of genes responsive to As is significative for figuring out this issue. Here, we identified a bHLH transcription factor OsbHLH6 that was involved in mediating the processes of As tolerance, uptake, and root-to-shoot translocation in rice. The expression of OsbHLH6 gene was strongly induced after 3 and 48 h of arsenite [As(III)] treatment. The OsbHLH6-overexpressed transgenic rice (OE-OsbHLH6) was sensitive to, while the knockout mutant of OsbHLH6 gene (Osbhlh6) was tolerant to As(III) stress by affecting the contents of reactive oxygen species (ROS) and non-protein thiols (NPT), etc. Knockout of OsbHLH6 gene increased significantly the As concentration in roots, but decreased extensively As accumulation in shoots, compared to that in OE-OsbHLH6 and WT plants. The transcripts of phytochelatins (PCs) synthetase encoding genes OsPCS1 and OsPCS2, as well as As(III) transporter encoding genes OsLsi1 and OsABCC1 were greatly abundant in Osbhlh6 mutants than in OE-OsbHLH6 and WT plants under As(III) stress. In contrast, the expression of OsLsi2 gene was extensively suppressed by As(III) in Osbhlh6 mutants. OsbHLH6 acted as a transcriptional activator to bind directly to the promoter and regulate the expression of OsPrx2 gene that encodes a peroxidase precursor. Moreover, overexpression of OsbHLH6 gene resulted in significant change of expression of amounts of abiotic stress-related genes, which might partially contribute to the As sensitivity of OE-OsbHLH6 plants. These findings may broaden our understanding of the molecular mechanism of OsbHLH6-mediated As response in rice and provide novel useful genes for rice As stress-resistant breeding.
砷（As）对植物具有极高的毒性，这对食品安全构成了严重威胁。鉴定对砷有响应的基因对于解决这一问题具有重要意义。在此，我们鉴定出一个bHLH转录因子OsbHLH6，它参与介导水稻对砷的耐受、吸收以及从根到地上部的转运过程。亚砷酸盐[As(III)]处理3小时和48小时后，OsbHLH6基因的表达被强烈诱导。过表达OsbHLH6的转基因水稻（OE-OsbHLH6）对As(III)胁迫敏感，而OsbHLH6基因的敲除突变体（Osbhlh6）通过影响活性氧（ROS）和非蛋白硫醇（NPT）等的含量来耐受As(III)胁迫。与OE-OsbHLH6和野生型植株相比，敲除OsbHLH6基因显著增加了根部的砷浓度，但大幅降低了地上部的砷积累量。在As(III)胁迫下，编码植物螯合肽（PCs）合成酶的基因OsPCS1和OsPCS2以及编码As(III)转运蛋白的基因OsLsi1和OsABCC1在Osbhlh6突变体中的转录本比在OE-OsbHLH6和野生型植株中丰富得多。相反，在Osbhlh6突变体中，As(III)广泛抑制了OsLsi2基因的表达。OsbHLH6作为转录激活因子直接结合到启动子上，并调控编码过氧化物酶前体的OsPrx2基因的表达。此外，过表达OsbHLH6基因导致大量非生物胁迫相关基因的表达发生显著变化，这可能部分导致了OE-OsbHLH6植株对砷的敏感性。这些发现可能拓宽我们对水稻中OsbHLH6介导的砷响应分子机制的理解，并为水稻抗砷胁迫育种提供新的有用基因。
