Jasmonic Acid Antagonizes Brassinosteroid-Induced The Increase Of Lamina Joint Angle And Regulates Cytoplastic Male Sterile Phenotype In Rice

Jasmonates (JAs), one class of plant hormones, regulate plant developmental processes including regulation of seed germination and seedling growth, induction of potato tubers formation and rice floret opening. JAs are also involved in the resistance of plants to biotic and abiotic stresses.In this paper, the plants of Wuxianggeng 14, Nipponbare, Yangdao 6 et al. rice species were used as experimental material to study the interactions between jasmonic acid (JA) and brassinosteroid (BR) in the regulation of rice lamina joint angle. The results indicated that there was difference on the second leaf angle among different plants of rice species during the natural growth process. High concentrations of methyl jasmonate (MeJA) could reduce lamina joint angle. Furthmore MeJA could inhibite 24-epibrassinolide (eBL)-induced leaf inclination. YCZ(RS-1-[[2-(2,4-dichlorophenyl)-4-(2-(2-propenyloxy) phenoxymethyl)-1,3-dioxolan-2-yl]methyl]1H-1,2,4-triazole), a BR biosynthesis inhibitor, reduced the leaf angle on higher concentrations.When seedlings treated with 0.1μg·μL-1 YCZ and different concentrations of MeJA, YCZ enhanced the inhibition effect of MeJA on the leaf angle.LiCl was widely used to block the activity of BIN2 kinase and it could increase the leaf angle. The inhibition of MeJA on the leaf angle was reduced by LiCl. These results suggest that MeJA could antagonize BR-induced the increase of lamina joint angle. The effect of MeJA may do not depend on the biosynthesis pathway of BR and MeJA may act upstream of BIN2 or act via another pathway independent on BIN2.Rice cytoplastic male sterile line Xieqingzao A (XqzA) and its maintainer line Xieqingzao B (XqzB) were used as materials to study the involvement of JA in cytoplasmic male sterility (CMS).JA-inhibited seed germination and seedling growth and JA-induced detached leaf senescence were used to compare the sensitivity of plant tissues to JA. In addition, wounding induced endogenous JA synthesis and change of endogenous JA level during the young panicle developmental period were used to compare JA production between these two lines. The results showed that higher concentrations of exogenous MeJA significantly inhibited seed germination on XqzA, but had no effect on XqzB, suggesting that MeJA exhibited stronger inhibition on seed germination in XqzA. While as to MeJA inhibited the second leaf growth, XqzB conferred a greater repression compared to XqzA. In terms of MeJA antagonizing eBL-induced the increase of lamina joint angle, XqzB conferred a greater sensitivity compared to XqzA. There was no difference in MeJA induced detached leaf senescence between these two lines. In addition, we also found that there was a greater increase of JA level in line B compared to line A after wounding. During the young panicle developmental period, more JA accumulation was found at the pollen mother cells meiosis stage in XqzA compared with XqzB, at which stage the pollen abortion occurs in XqzA. No obvious difference between XqzA and XqzB was observed at other stages examined. These results indicate that sensitivity of plant to JA has tissues and developmental specificity and that the poor level of JA in XqzA may be one of the reasons that cause cytoplasmic male sterile during the pollen abortion period.In conclusions, MeJA could antagonize BR-induced the increase of lamina joint angle. The effect of MeJA may do not depend on the biosynthesis pathway of BR and MeJA may act upstream of BIN2 or act via another pathway independent on BIN2. Sensitivity of rice seeding to JA has tissues and developmental specificity. During the pollen abortion period, the poor level of JA in XqzA may be one of the reasons that cause cytoplasmic male sterile.