Division of Science for Bioresources, Graduate School of Environment and Life Science, Okayama University, 2-20-1 Chuo, Kurashiki, 710-0046 Japan.
Institute of Plant Science and Resources, Okayama University, 2-20-1 Chuo, Kurashiki, 710-0046 Japan.
Plant Cell Physiol. 2020 Mar 1;61(3):470-480. doi: 10.1093/pcp/pcz212.
Regulation of the stability and the quality of mitochondrial RNA is essential for the maintenance of mitochondrial and cellular functions in eukaryotes. We have previously reported that the eukaryotic poly(A)-specific ribonuclease (PARN) and the prokaryotic poly(A) polymerase encoded by AHG2 and AGS1, respectively, coordinately regulate the poly(A) status and the stability of mitochondrial mRNA in Arabidopsis. Mitochondrial function of PARN has not been reported in any other eukaryotes. To know how much this PARN-based mitochondrial mRNA regulation is conserved among plants, we studied the AHG2 and AGS1 counterparts of the liverwort, Marchantia polymorpha, a member of basal land plant lineage. We found that M. polymorpha has one ortholog each for AHG2 and AGS1, named MpAHG2 and MpAGS1, respectively. Their Citrine-fused proteins were detected in mitochondria of the liverwort. Molecular genetic analysis showed that MpAHG2 is essential and functionally interacts with MpAGS1 as observed in Arabidopsis. A recombinant MpAHG2 protein had a deadenylase activity in vitro. Overexpression of MpAGS1 and the reduced expression of MpAHG2 caused an accumulation of polyadenylated Mpcox1 mRNA. Furthermore, MpAHG2 suppressed Arabidopsis ahg2-1 mutant phenotype. These results suggest that the PARN-based mitochondrial mRNA regulatory system is conserved in land plants.
真核生物中线粒体 RNA 的稳定性和质量的调节对于维持线粒体和细胞功能至关重要。我们之前曾报道，真核多聚（A）特异性核糖核酸酶（PARN）和由 AHG2 和 AGS1 分别编码的原核多聚（A）聚合酶，在拟南芥中协调调节多聚（A）状态和线粒体 mRNA 的稳定性。在其他真核生物中尚未报道过 PARN 的线粒体功能。为了了解这种基于 PARN 的线粒体 mRNA 调节在植物中保存了多少，我们研究了基生植物谱系成员 Marchantia polymorpha 的 AHG2 和 AGS1 的对应物。我们发现 M. polymorpha 分别有一个 AHG2 和 AGS1 的直系同源物，分别命名为 MpAHG2 和 MpAGS1。它们的 Citrine 融合蛋白在该植物的线粒体中被检测到。分子遗传学分析表明，MpAHG2 是必需的，并与在拟南芥中观察到的 MpAGS1 功能相互作用。重组的 MpAHG2 蛋白在体外具有脱腺苷酸酶活性。MpAGS1 的过表达和 MpAHG2 的表达减少导致多聚腺苷酸化的 Mpcox1 mRNA 的积累。此外，MpAHG2 抑制了拟南芥 ahg2-1 突变体的表型。这些结果表明，基于 PARN 的线粒体 mRNA 调节系统在陆地植物中是保守的。
