Identification of an AtCRN1-like chloroplast protein BeCRN1 and its distinctive role in chlorophyll breakdown during leaf senescence in bamboo (Bambusa emeiensis ‘Viridiflavus’)

CRN1/PPH/NYC3 is one of the key genes responsible for chlorophyll degradation during senescence in both Arabidopsis and rice. In this study, BeCRN1 and its promoter, BeCRN1p , were isolated from, Bambusa emeiensis ‘Viridiflavus’ , a bamboo variety, for the first time. BeCRN1 consists of 1,646 bp, with an open reading frame of 1,473 bp, encoding a predicted polypeptide of 490 amino acids. Besides, BeCRN1 contained 5 exons and 4 introns, and harbored a distinctive microsatellite in the fourth intron. Differences in BeCRN1p are observed primarily in the AtCRN1 promoter, while sharing similar cis element composition with the rice CRN1 promoter. BeCRN1 is localized within the chloroplast, and it is strongly induced by senescence signals. Although constitutive overexpression of BeCRN1 in crn1 has reversed the stay-green phenotype of crn1 to the wild type phenotype, its promoter has failed to do so with AtCRN1 following dark treatment. The efficiency of BeCRN1p is only about one-third of that of the AtCRN1 promoter.