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Mg-chelatase I subunit 1 and Mg-protoporphyrin IX methyltransferase affect the stomatal aperture in Arabidopsis thaliana

Author:
Tomiyama, Masakazu, Inoue, Shin-ichiro, Tsuzuki, Tomo, Soda, Midori, Morimoto, Sayuri, Okigaki, Yukiko, Ohishi, Takaya, Mochizuki, Nobuyoshi, Takahashi, Koji, Kinoshita, Toshinori
Source:
Journal of plant research 2014 v.127 no.4 pp. 553-563
ISSN:
0918-9440
Subject:
Arabidopsis thaliana, abscisic acid, chlorophyll, gene expression, genes, leaves, loci, magnesium protoporphyrin IX methyltransferase, missense mutation, mutants, phenotype, seedlings, stomata, stomatal movement, temperature, thermography
Abstract:
To elucidate the molecular mechanisms of stomatal opening and closure, we performed a genetic screen using infrared thermography to isolate stomatal aperture mutants. We identified a mutant designated low temperature with open-stomata 1 (lost1), which exhibited reduced leaf temperature, wider stomatal aperture, and a pale green phenotype. Map-based analysis of the LOST1 locus revealed that the lost1 mutant resulted from a missense mutation in the Mg-chelatase I subunit 1 (CHLI1) gene, which encodes a subunit of the Mg-chelatase complex involved in chlorophyll synthesis. Transformation of the wild-type CHLI1 gene into lost1 complemented all lost1 phenotypes. Stomata in lost1 exhibited a partial ABA-insensitive phenotype similar to that of rtl1, a Mg-chelatase H subunit missense mutant. The Mg-protoporphyrin IX methyltransferase (CHLM) gene encodes a subsequent enzyme in the chlorophyll synthesis pathway. We examined stomatal movement in a CHLM knockdown mutant, chlm, and found that it also exhibited an ABA-insensitive phenotype. However, lost1 and chlm seedlings all showed normal expression of ABA-induced genes, such as RAB18 and RD29B, in response to ABA. These results suggest that the chlorophyll synthesis enzymes, Mg-chelatase complex and CHLM, specifically affect ABA signaling in the control of stomatal aperture and have no effect on ABA-induced gene expression.
Agid:
362364