Meng Wei, Xu Lijian, Du Zhi-Yan, Wang Fang, Zhang Rui, Song Xingshun, Lam Sin Man, Shui Guanghou, Li Yuhua, Chye Mee-Len
Key Laboratory of Saline-alkali Vegetation Ecology Restoration (Northeast Forestry University), Ministry of Education, Harbin, 150040, China.
College of Life Science, Northeast Forestry University, Harbin, 150040, China.
Rice (N Y). 2020 Nov 6;13(1):75. doi: 10.1186/s12284-020-00435-y.
Acyl-coenzyme A (CoA) esters are important intermediates in lipid metabolism with regulatory properties. Acyl-CoA-binding proteins bind and transport acyl-CoAs to fulfill these functions. RICE ACYL-COA-BINDING PROTEIN6 (OsACBP6) is currently the only one peroxisome-localized plant ACBP that has been proposed to be involved in β-oxidation in transgenic Arabidopsis. The role of the peroxisomal ACBP (OsACBP6) in rice (Oryza sativa) was investigated.
Here, we report on the function of OsACBP6 in rice. The osacbp6 mutant showed diminished growth with reduction in root meristem activity and leaf growth. Acyl-CoA profiling and lipidomic analysis revealed an increase in acyl-CoA content and a slight triacylglycerol accumulation caused by the loss of OsACBP6. Comparative transcriptomic analysis discerned the biological processes arising from the loss of OsACBP6. Reduced response to oxidative stress was represented by a decline in gene expression of a group of peroxidases and peroxidase activities. An elevation in hydrogen peroxide was observed in both roots and shoots/leaves of osacbp6. Taken together, loss of OsACBP6 not only resulted in a disruption of the acyl-CoA homeostasis but also peroxidase-dependent reactive oxygen species (ROS) homeostasis. In contrast, osacbp6-complemented transgenic rice displayed similar phenotype to the wild type rice, supporting a role for OsACBP6 in the maintenance of the acyl-CoA pool and ROS homeostasis. Furthermore, quantification of plant hormones supported the findings observed in the transcriptome and an increase in jasmonic acid level occurred in osacbp6.
In summary, OsACBP6 appears to be required for the efficient utilization of acyl-CoAs. Disruption of OsACBP6 compromises growth and led to provoked defense response, suggesting a correlation of enhanced acyl-CoAs content with defense responses.
酰基辅酶A（CoA）酯是脂质代谢中的重要中间体，具有调节特性。酰基辅酶A结合蛋白结合并转运酰基辅酶A以实现这些功能。水稻酰基辅酶A结合蛋白6（OsACBP6）是目前唯一一种定位于过氧化物酶体的植物ACBP，已有人提出它参与转基因拟南芥的β-氧化过程。本研究对水稻（Oryza sativa）中过氧化物酶体ACBP（OsACBP6）的作用进行了探究。
在此，我们报道了OsACBP6在水稻中的功能。osacbp6突变体生长减弱，根分生组织活性和叶片生长降低。酰基辅酶A谱分析和脂质组学分析表明，OsACBP6缺失导致酰基辅酶A含量增加和三酰甘油略有积累。比较转录组分析识别出因OsACBP6缺失而产生的生物学过程。一组过氧化物酶的基因表达下降和过氧化物酶活性降低表明对氧化应激的反应减弱。在osacbp6的根和地上部/叶片中均观察到过氧化氢水平升高。综上所述，OsACBP6的缺失不仅导致酰基辅酶A稳态的破坏，还导致过氧化物酶依赖性活性氧（ROS）稳态的破坏。相比之下，osacbp6互补转基因水稻表现出与野生型水稻相似的表型，支持OsACBP6在维持酰基辅酶A库和ROS稳态中的作用。此外，植物激素定量分析支持了转录组中的发现，并且osacbp6中茉莉酸水平升高。
总之，OsACBP6似乎是有效利用酰基辅酶A所必需的。OsACBP6的破坏会损害生长并引发防御反应，表明酰基辅酶A含量增加与防御反应之间存在关联。
