AUTHOR=Wu Cai-jun , Wang Jie , Zhu Jun , Ren Jing , Yang You-xin , Luo Tao , Xu Lu-xi , Zhou Qing-hong , Xiao Xu-feng , Zhou Yu-xin , Luo Sha 

TITLE=Molecular Characterization of Mg-Chelatase CHLI Subunit in Pea (Pisum sativum L.)

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.821683

DOI=10.3389/fpls.2022.821683

ISSN=1664-462X

ABSTRACT=<p>As a rate-limiting enzyme for chlorophyll biosynthesis, Mg-chelatase is a promising target for improving photosynthetic efficiency. It consists of CHLH, CHLD, and CHLI subunits. In pea (<italic>Pisum sativum</italic> L.), two putative <italic>CHLI</italic> genes (<italic>PsCHLI1</italic> and <italic>PsCHLI2</italic>) were revealed recently by the whole genome sequencing, but their molecular features are not fully characterized. In this study, <italic>PsCHLI1</italic> and <italic>PsCHLI2</italic> cDNAs were identified by PCR-based cloning and sequencing. Phylogenetic analysis showed that PsCHLIs were derived from an ancient duplication in legumes. Both <italic>PsCHLIs</italic> were more highly expressed in leaves than in other organs and downregulated by abscisic acid and heat treatments, while <italic>PsCHLI1</italic> was more highly expressed than <italic>PsCHLI2</italic>. <italic>PsCHLI1</italic> and <italic>PsCHLI2</italic> encode 422- and 417-amino acid proteins, respectively, which shared 82% amino acid identity and were located in chloroplasts. Plants with a silenced <italic>PsCHLI1</italic> closely resembled <italic>PsCHLI1</italic> and <italic>PsCHLI2</italic> double-silenced plants, as both exhibited yellow leaves with barely detectable Mg-chelatase activity and chlorophyll content. Furthermore, plants with a silenced <italic>PsCHLI2</italic> showed no obvious phenotype. In addition, the N-terminal fragment of PsCHLI1 (PsCHLI1N, Val63-Cys191) and the middle fragment of PsCHLI1 (PsCHLI1M, Gly192-Ser336) mediated the formation of homodimers and the interaction with CHLD, respectively, while active PsCHLI1 was only achieved by combining PsCHLI1N, PsCHLI1M, and the C-terminal fragment of PsCHLI1 (Ser337-Ser422). Taken together, PsCHLI1 is the key CHLI subunit, and its peptide fragments are essential for maintaining Mg-chelatase activity, which can be used to improve photosynthetic efficiency by manipulating Mg-chelatase in pea.</p>