Abstract
In Arabidopsis, the ethylene-receptor signal output occurs at the endoplasmic reticulum and is mediated by the Raf-like protein CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) but is prevented by overexpression of the CTR1 N terminus. A phylogenic analysis suggested that rice OsCTR2 is closely related to CTR1, and ectopic expression of CTR1p:OsCTR2 complemented Arabidopsis ctr1-1. Arabidopsis ethylene receptors ETHYLENE RESPONSE1 and ETHYLENE RESPONSE SENSOR1 physically interacted with OsCTR2 on yeast two-hybrid assay, and green fluorescence protein-tagged OsCTR2 was localized at the endoplasmic reticulum. The osctr2 loss-of-function mutation and expression of the 35S:OsCTR2 1–513 transgene that encodes the OsCTR2 N terminus (residues 1–513) revealed several and many aspects, respectively, of ethylene-induced growth alteration in rice. Because the osctr2 allele did not produce all aspects of ethylene-induced growth alteration, the ethylene-receptor signal output might be mediated in part by OsCTR2 and by other components in rice. Yield-related agronomic traits, including flowering time and effective tiller number, were altered in osctr2 and 35S:OsCTR2 1–513 transgenic lines. Applying prolonged ethylene treatment to evaluate ethylene effects on rice without compromising rice growth is technically challenging. Our understanding of roles of ethylene in various aspects of growth and development in japonica rice varieties could be advanced with the use of the osctr2 and 35S:OsCTR2 1–513 transgenic lines.
Highlights
Ethylene, a gaseous plant hormone, regulates many aspects of plant growth and development, such as responses to stress and pathogens, fruit ripening, senescence, (Anderson et al, 2004), and cell elongation (Alonso and Granell, 1995; Hua and Meyerowitz, 1998; Alexander and Grierson, 2002)
To identify proteins related to Arabidopsis CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) in rice, we performed a BLAST search and identified 64 CTR1-related proteins from 25 plant species for phylogenetic analysis
Within the CTR1 clade, Arabidopsis CTR1 and CTR1-related proteins from dicotyledonous plant species were in the same subclade, and OsCTR1/OsCTR2 and CTR1-related proteins from monocotyledonous plants were in another subclade
Summary
A gaseous plant hormone, regulates many aspects of plant growth and development, such as responses to stress and pathogens, fruit ripening, senescence, (Anderson et al, 2004), and cell elongation (Alonso and Granell, 1995; Hua and Meyerowitz, 1998; Alexander and Grierson, 2002). Many studies have used mainly dicotyledonous plants to investigate the effects of ethylene. Previous studies of the ethylene effects on rice have focused mostly on flooding responses in a few specific varieties of the inidca rice cultivar. In varieties of indica floating rice ( called deep-water rice), flooding induces a burst of ethylene biosynthesis, which promotes gibberellin biosynthesis and abscisic acid degradation (van der Knaap et al, 2000; Saika et al, 2007; Fukao and Bailey-Serres, 2008a). Gibberellin treatment can replace ethylene treatment to induce internodal elongation in deep-water rice varieties, so rapid rice growth
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