Functional Analyses Of OsJMJ714 In Lateral Root Development

Histone lysine methylation is an important epigenetic modification and plays key roles in regulating gene expression. In animals, JmjC domain containing proteins have histone demethylase activity, and the JmjC domain is their essentil catalytic domain. In rice, at least 20 JmjC proteins have been identified and belong to four subfamilies. Among of these proteins, JmjC domain only family contains seven proteins with JmjC domains only. Except for OsJMJ760, the functions of the other members are unclear. In this study, the character of OsJMJ714 and its function in regulating rice root initiation and development was discussed.OsJMJ714 contains conserved residues required for Fe (II) andαKG binding. In addition, OsJMJ714 reduced the methylation level of H3K9me1/2/3 in vivo and in vitro. It suggests that OsJMJ714 is a histon demethylase. At the transcription level, we found that the expression of OsJMJ714 in root was higher than those in leaf and shoot. Moreover, its expression was rapidly induced by different salt treatments. These results suggested that OsJMJ714 might be involved in regulating the initiation and development of root as well as rice response to salt stress.To investigate the regulatory function of OsJMJ714 in rice, we generated transgenetic rice plants overexpressing OsJMJ714. Under normal condition, many lateral roots were observed in WT within 3 days, whereas, few lateral roots were found in transgenetic plants. The results implied that OsJMJ714 might play important roles in regulating lateral root initiational and developmental progresses in rice.We further compared the DNA methylation pattern between transgentic and WT rice using MSAP method. Our results showed that overexpression OsJMJ714 in rice increase the methylation level of genome DNA. Moreover, the expression level of NAC family genes ( AK099237,AK068501) and Os05g46000 (encoding a DNA glycosylase family protein) was lower in OsJMJ714 transgenic lines than that in WT plants.It was reported that the biosynthesis, stability, transport and signal transduction of auxin and cytokinin were involved in the regulation of root growth and development in rice. Our analyses showed that NAA recovered the difference of small lateral root between transgenic rice and WT. More over, the development of small lateral root in transgenic plant is insecitive to 6-BA. Further, the transcription level of OsYUCCAs, OsIPTs and OsRRs was down-regulated in transgenetic lines compared with that in WT plants.Taken together, we thought that OsJMJ714 might participate in the modification of genome DNA methylation and H3K9 demethylation, which resulted in the change of the expression level of many genes, and finally affected the root growth and development in transgenetic rice.