Jasmonic acid negatively regulation of root growth in Japonica rice (Oryza sativa L.) under cadmium treatment

To explore the role of jasmonic acid (JA) in seed germination of japonica rice under Cadmium (Cd) stress, the growth indices of japonica rice varieties under the bud stage were measured for identifying the variety difference in Cd tolerance. Then the tolerant variety JJ818 and the sensitive one NJ9108 were treated under 150 mu mol L-1 Cd concentration, 0.5 mu mol L-1 methyl jasmonate (MeJA), and 10 mu mol L-1 Ibuprofen (IBU) alone or in combination to study the molecular mechanism. In addition to the germination phenotype (germination rate, root length and bud length), soluble protein content, soluble sugar content, and sugar components, alpha-amylase activity, and its related gene expression were also measured. The results showed that Cd treatment restricted the root length of rice seed (P < 0.05) but had little effect on germination rate and shoot length. The combined application of MeJA with Cd treatment further reduced the seed germination rate and shoot length, while its inhibitor (Ibuprofen) treatment showed an opposite trend. Cd treatment also decreased the expression of the alpha Amy and RL1, and the accompanying increases of the gene expression of JIOsPR10, OsLOX1, and OsLOX4 related to synthesizing JA. The results indicated that JA negatively regulates the of root growth of japonica rice seeds under cadmium treatment via the genes related to the synthesis at the bud stage. Compared with the NJ9108, JJ818 was more tolerant to Cd stress and was related to its insensitivity to JA.