Jasmonate regulates juvenile-adult phase transition in rice

Abstract

Juvenile-adult phase transition is an important shift for the acquisition of adult vegetative character and subsequent reproductive competence. We identified a recessive precocious (pre) mutant exhibiting long leaf phenotype in rice. The long leaf phenotype is conspicuous in 2nd through 4th leaves that are juvenile and juvenile-adult transition leaves. We found that the morphological and physiological traits such as the midrib formation, shoot meristem size, photosynthetic rate and plastochron in juvenile and juvenile-adult transition stages of pre have precociously acquired adult characters. In agreement with these results, expression patterns of miR156 and miR172, which are microRNAs regulating phase change, support the accelerated juvenile-adult phase change in pre. The PRE gene encodes an allene oxide synthase (OsAOS1), which is a key enzyme for the biosynthesis of jasmonic acid (JA). pre mutant showed a low level of JA and enhanced sensitivity to gibberellic acid promoting the phase change in some plant species. We also show that prolonged plastochron in pre is caused by the accelerated PLASTOCHRON1 (PLA1) function. The present study reveals a substantial role of JA as a negative regulator of vegetative phase change.