在熱逆境下阿拉伯芥中miR164與miR173的調節功能

Abstract

近年研究指出，microRNA (miRNA) 在植物遭受逆境時，表現量會快速的變化以調控植物對逆境的適應性；然而，目前miRNA調控熱逆境反應的相關研究並不多。在本研究中，首先以DNA微陣列 (microarray) 分析，發現有兩群基因在熱處理下會有反應，分別為miR173以及miR164的目標基因。利用即時定量PCR與北方墨點法確認在熱逆境下，miR164表現量會上升，而miR164的目標基因CUC1、CUC2、NAC1、ANAC092與At3g12977會被抑制；相反的，miR173表現會下降，其中miR173的目標基因At4g29770和At5g18040表現情形則會與miR173相反。此外，mir164a T-DNA突變株在長時間熱逆境下會有明顯不耐熱的性狀。並且，也發現mir164 a和mir164b T-DNA突變株在高溫下，熱休克蛋白HSP21以及HSP17.6表現量都較野生型植株低。而在miR173的研究中，則是大量表現miR173植株會呈現對熱較為敏感的性狀，但是熱休克蛋白的表現與野生型植株的則沒有明顯差異。綜合實驗的結果得知，在高溫逆境下，植物缺乏miR164a時，植物中的miR164無法有效的抑制目標基因，並影響HSP21和HSP17.6的表現，使植物無法耐受熱逆境；而miR173則是在高溫下會被抑制，並以未知的方式來幫助植物抵抗熱逆境。

MicroRNAs (miRNAs) are considered as an integral part of plant stress regulatory networks. However, limited research has been conducted on the heat-responsive miRNAs. In this study , microarray analyses were used to examine the changes of gene profile under heat stress. Two groups of genes responding to heat stress were obtained, and they were targeted by miR164 and miR173, respectively. Quantitative RT-PCR and northern blotting reveal that the amount of miR164 was accumulated when plants were treated with heat stress, whereas its target genes CUC1, CUC2, NAC1, ANAC092, and At3g12977 were repressed. However, the expression of miR173 was reduced by heat treatment, and two of its target genes, At4g29770 and At5g18040, were induced upon heat treatment. In the phenotypic analyses, mir164a T-DNA insertion lines were more sensitive to heat than wild-type plant in the long-term heat stress. In addition, the expression of HSP21 and HSP17.6 was reduced in mir164a and mir164b T-DNA lines compared to those in wild-type plant after heat treatment. Contrary to miR164 responses, miR173 overexpression lines were more sensitive to heat stress than wild-type. But, HSPs expression showed no significantly different between miR173 transgenics and wild-type. Taken together, miR164 and miR173 were involved in heat tolerance either through regulating HSPs or specific target genes in an unknown pathway.