Lamina joint inclination or leaf angle (the angle between the leaf blade and vertical culm) is a major
trait of rice plant architecture. The plant hormone brassinosteroid (BR) is the main regulator of this trait,
while other plant hormones, including ethylene, gibberellin, and auxin, also influence leaf angle. In this
study, we found that methyl jasmonate (MeJA) also participates in regulating lamina joint inclination.
MeJA decreased lamina jointinclination and inhibited the BR-induced increase in lamina jointinclination.
Furthermore, addition of a BR synthesis inhibitor increased the extent of change in lamina jointinclination
in response to treatment with a low concentration of MeJA (0.05 or 0.5 mg L−1), but it did not alter the
lamina joint inclination of plants treated with a high concentration of MeJA (5 mg L−1). Further studies
showed that MeJA treatment significantly repressed the expression of BR biosynthesis-related genes and
decreased endogenous BRs levels. In addition,the lamina jointinclination in the OsBRI1 mutant d61-1 was
less sensitive to MeJA compared with its wild type counterpart, and lithium chloride-induced inactivation
of GSK3-like kinase, a negative regulator of BR signaling, partly rescued the MeJA-induced reduction in
lamina joint inclination. Further studies showed that MeJA treatment reduced the mRNA levels of BR
signaling and target genes. These results indicate that MeJA-inhibition of lamina joint inclination may
depend on BR biosynthesis and the BR signaling pathway.
© 2015 Elsevier Ireland Ltd. All rights reserved.
Lamina joint inclination or leaf angle (the angle between the leaf blade and vertical culm) is a majortrait of rice plant architecture. The plant hormone brassinosteroid (BR) is the main regulator of this trait,while other plant hormones, including ethylene, gibberellin, and auxin, also influence leaf angle. In thisstudy, we found that methyl jasmonate (MeJA) also participates in regulating lamina joint inclination.MeJA decreased lamina jointinclination and inhibited the BR-induced increase in lamina jointinclination.Furthermore, addition of a BR synthesis inhibitor increased the extent of change in lamina jointinclinationin response to treatment with a low concentration of MeJA (0.05 or 0.5 mg L−1), but it did not alter thelamina joint inclination of plants treated with a high concentration of MeJA (5 mg L−1). Further studiesshowed that MeJA treatment significantly repressed the expression of BR biosynthesis-related genes anddecreased endogenous BRs levels. In addition,the lamina jointinclination in the OsBRI1 mutant d61-1 wasless sensitive to MeJA compared with its wild type counterpart, and lithium chloride-induced inactivationof GSK3-like kinase, a negative regulator of BR signaling, partly rescued the MeJA-induced reduction inlamina joint inclination. Further studies showed that MeJA treatment reduced the mRNA levels of BRsignaling and target genes. These results indicate that MeJA-inhibition of lamina joint inclination maydepend on BR biosynthesis and the BR signaling pathway.© 2015 Elsevier Ireland Ltd. All rights reserved.
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