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J Plant Res (2014) 127:553563 DOI 10.1007/s10265-014-0636-0
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Mg-chelatase I subunit 1 and Mg-protoporphyrin IX methyltransferase affect the stomatal aperturein Arabidopsis thaliana
Masakazu Tomiyama Shin-ichiro Inoue Tomo Tsuzuki Midori Soda
Sayuri Morimoto Yukiko Okigaki Takaya Ohishi Nobuyoshi Mochizuki
Koji Takahashi Toshinori Kinoshita
Received: 17 October 2013 / Accepted: 26 March 2014 / Published online: 20 May 2014 The Botanical Society of Japan and Springer Japan 2014
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 identied 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 mis-sense 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, specically affect ABA signaling in the control of stomatal aperture and have no effect on ABA-induced gene expression.
Keywords ABA Arabidopsis thaliana Infrared
thermography Mg-chelatase I subunit 1 Mg
protoporphyrin IX methyltransferase Stomatal guard cells
Introduction
Stomatal pores in the plant epidermis, each surrounded by a pair of guard cells, regulate gas exchange between plants and the atmosphere to control processes such as CO2 uptake for photosynthesis and transpiration for water loss regulation (Shimazaki et al. 2007). Stomatal opening is induced by light, whereas stomatal closure is induced by the phytohormone abscisic acid (ABA), which is synthesized in response to drought stress (Assmann and Shimazaki 1999; Schroeder et al. 2001). ABA-induced stomatal closure is driven by an efux of K? from guard cells through outward-rectifying K?...