title: CHLH/GUN5 Function in Tetrapyrrole Metabolism Is Correlated with Plastid Signaling but not ABA Responses in Guard Cells.
abstract: Expression ofPhotosynthesis-Associated Nuclear Genes(PhANGs) is controlled by environmental stimuli and plastid-derived signals ("plastid signals") transmitting the developmental and functional status of plastids to the nucleus.Arabidopsis genomes uncoupled(gun) mutants exhibit defects in plastid signaling, leading to ectopic expression ofPhANGsin the absence of chloroplast development.GUN5encodes the plastid-localized Mg-chelatase enzyme subunit (CHLH), and recent studies suggest that CHLH is a multifunctional protein involved in tetrapyrrole biosynthesis, plastid signaling and ABA responses in guard cells. To understand the basis of CHLH multifunctionality, we investigated 15gun5missense mutant alleles and transgenic lines expressing a series of truncated CHLH proteins in a severegun5allele (cch) background (tCHLHs, 10 different versions). Here, we show that Mg-chelatase function and plastid signaling are generally correlated; in contrast, based on the analysis of thegun5missense mutant alleles, ABA-regulated stomatal control is distinct from these two other functions. We found that none of the tCHLHs could restore plastid-signaling or Mg-chelatase functions. Additionally, we found that both the C-terminal half and N-terminal half of CHLH function in ABA-induced stomatal movement.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University Kyoto, Japan.
authors.forename: Harue
authors.initials: H
authors.lastname: Ibata
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University Kyoto, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Nagatani
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University Kyoto, Japan.
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Mochizuki
keywords: CHLH; GUN5; Mg-chelatase; plastid signal; stomatal ABA response; tetrapyrrole