Juvenile-to-adult phase transition is an important shift for the acquisition of adult vegetative characteristics and subsequent reproductive competence. We identified a recessive precocious (pre) mutant exhibiting a long leaf phenotype in rice. The long leaf phenotype is conspicuous in the second to the fourth leaves, which are juvenile and juvenile-to-adult transition leaves. We found that morphological and physiological traits, such as midrib formation, shoot meristem size, photosynthetic rate and plastochron, in juvenile and juvenile-to-adult transition stages of the pre mutant have precociously acquired adult characteristics. In agreement with these results, expression patterns of miR156 and miR172, which are microRNAs regulating phase change, support the accelerated juvenile-to-adult phase change in the pre mutant. The mutated gene encodes an allene oxide synthase (OsAOS1), which is a key enzyme for the biosynthesis of jasmonic acid (JA). The pre mutant showed a low level of JA and enhanced sensitivity to gibberellic acid, which promotes the phase change in some plant species. We also show that prolonged plastochron in the pre mutant is caused by accelerated PLASTOCHRON1 (PLA1) function. The present study reveals a substantial role of JA as a negative regulator of vegetative phase change.
The authors declare no competing or financial interests.
K.-i.H., J.-i.I. and Y.N. designed experiments. K.-i.H. and M.I. carried out the majority of the experiments. K.-i.H., M.I., M.M., N.S., M.K., H.S. and T.Y. carried out experiments, analyzed and interpreted data. K.-i.H., Y.K. and Y.N. wrote the paper. All authors read and commented on the manuscript prior to submission.
This work was supported in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan [23658005 to Y.N. and K.-i.H. and 24380005 to J.-i.I.].
Sequence data for PRE (OsAOS1) (Os03g0767000) complete cDNA and protein can be found in the GenBank data libraries under accession number LC163980 (available at: https://www.ncbi.nlm.nih.gov/nuccore/LC163980).
Supplementary information available online at http://dev.biologists.org/lookup/doi/10.1242/dev.138602.supplemental
- Received April 13, 2016.
- Accepted August 4, 2016.