Mg-chelatase I subunit 1 and Mg-protoporphyrin IX methyltransferase affect the stomatal aperture in Arabidopsis thaliana.
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.
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya, 464-8602, Japan.
Masakazu
M
Tomiyama
Shin-Ichiro
S
Inoue
Tomo
T
Tsuzuki
Midori
M
Soda
Sayuri
S
Morimoto
Yukiko
Y
Okigaki
Takaya
T
Ohishi
Nobuyoshi
N
Mochizuki
Koji
K
Takahashi
Toshinori
T
Kinoshita
D000040:Abscisic Acid / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000096:biosynthesis; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D054046:Plant Stomata / Q000201:enzymology*; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D013817:Thermography
D029681:Arabidopsis Proteins; D002734:Chlorophyll; D000040:Abscisic Acid; D008780:Methyltransferases; C000612820:CHLM protein, Arabidopsis; C060234:magnesium-protoporphyrin methyltransferase; D000251:Adenosine Triphosphatases; C000595157:CHLI1 protein, Arabidopsis