State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, 510642, Guangdong, China.
BMC Plant Biol. 2019 Mar 18;19(1):105. doi: 10.1186/s12870-019-1707-0.
NCA1 (NO CATALASE ACTIVITY 1) was recently identified in Arabidopsis as a chaperone protein to regulate catalase (CAT) activity through maintaining the folding of CAT. The gene exists mainly in higher plants; some plants, such as Arabidopsis, contain only one NCA1 gene, whereas some others such as rice harbor two copies. It is not yet understood whether and how both isoforms have functioned to regulate CAT activity in those two-copy-containing plant species.
In this study, we first noticed that the spatiotemporal expression patterns of NCA1a and NCA1b were very similar in rice plants. Subsequent BiFC and yeast three-hybrid experiments demonstrated that both NCA1a and NCA1b show mutually exclusive, rather than simultaneous, interaction with CAT. For a further functional analysis, nca1a and nca1b single mutants or double mutants of rice were generated by CRISPR/Cas9. Analysis on these mutants under both normal and salinity stress conditions found that, as compared with WT, either nca1a or nca1b single mutant showed no difference at phenotypes and CAT activities, whereas the double mutants constantly displayed very low CAT activity (about 5%) and serious lesion phenotypes.
These results suggest that NCA1a and NCA1b show mutually exclusive interaction with CAT to regulate CAT activity in a functionally-redundant manner in rice.
最近在拟南芥中发现 NCA1（无过氧化氢酶活性 1）是一种伴侣蛋白，通过维持过氧化氢酶（CAT）的折叠来调节 CAT 活性。该基因主要存在于高等植物中；一些植物，如拟南芥，只含有一个 NCA1 基因，而另一些植物，如水稻，含有两个拷贝。目前尚不清楚这两个同工酶是否以及如何在那些含有两个拷贝的植物物种中调节 CAT 活性。
在这项研究中，我们首先注意到 NCA1a 和 NCA1b 在水稻植株中的时空表达模式非常相似。随后的 BiFC 和酵母三杂交实验表明，NCA1a 和 NCA1b 与 CAT 相互排斥，而不是同时相互作用。为了进一步进行功能分析，我们通过 CRISPR/Cas9 生成了水稻的 nca1a 和 nca1b 单突变体或双突变体。在正常和盐胁迫条件下对这些突变体进行分析发现，与 WT 相比，nca1a 或 nca1b 单突变体在表型和 CAT 活性上没有差异，而双突变体始终表现出非常低的 CAT 活性（约 5%）和严重的损伤表型。
这些结果表明，NCA1a 和 NCA1b 以功能冗余的方式与 CAT 相互排斥，以调节 CAT 在水稻中的活性。
