The Function Of OsJMJ714in Regulation Of Root Development And Auxin Content In Rice

Histone lysine methylation is a dynamic and reverible process, which is controlled by coregulationof histone lysine methyltransferase and histone demethylase. Histone demethylase include two types:lysine specific demethylases1(LSD1) which uses FAD as a cofactor; JMJC proteins, containing JmjCfunctional domain, which use Fe2+and a-KG as cofactors and function as main histone demethylase. Atleast,20JmjC domain-containing protein genes have been identified in rice and divided into severalsubgroups. JMJ714belongs to JmjC-domain-only subgroup, which contain no other recognizableprotein domains apart from the JmjC domain. Our previous work has demonstrated that JMJ714contains conserved residues required for Fe2+and a-KG binding and can demethylate H3K9me1/2/3aswell as influence the lateral root initiation. But the characteristics and biological function of JMJ714still need further perfection.We firstly analyzed the expression characteristics of JMJ714through Q-PCR and GUS staining.Our results showed that the expression of JMJ714was induced by drought and20%PEG. Theexpression level of JMJ714was down-regulated under the treatment of salt, ABA,6-BA and NAA. Inaddition, JMJ714showed different expression levels in diverse development stages and tissues,especially displayed relative high expression levels in young tissues. Then we analyzed the subcellularlocalization of JMJ714throuhg transient expression of JMJ714-GFP fusion protein in onion epidermalcells. The results showed that JMJ714was localized in cell nuclei.To further explore the biological function of JMJ714, we analyzed its biological effect at differentdevelopment stages. We found that JMJ714transgenic plants displayed pleiotropic phenotypesincluding root morphology, height, flowering time, leaf shape and seed germination. Especially, JMJ714had obvious influence on rice root system development including the length and numbers of lateralroots and crown roots, the geotropism of radical roots. JMJ714-overexpressing lines showed decreasedlength and numbers of lateral roots and crown roots, as well as slight-geotropism of radical roots. Incontrast, JMJ714-RNAi lines exhibited an increase in length and numbers of lateral roots and crownroots, as well as curly radical roots. Moreover, JMJ714-overexpressing lines were less sensitive toexogenous a-NAA while JMJ714-RNAi lines were more sensitive to exogenous a-NAA. The currentresearch shows that auxin plays an important role in the process of lateral roots and crown rootsformation and that hyper auxin level may lead to curly roots. Furthermore, defect in auxin biosynthesisand/or metabolism usually causes impaired geotropism of the radical roots. Therefore, we suppose thatJMJ714may affect the IAA content in the rice root system which leads to the influence on rootmorphogenesis.To confirm our presumption, the IAA content and the expression level of auxin metabolism relatedgenes were detected in the JMJ714transgenic plants. At the transcription level, JMJ714positivelyregulated the expression of GH3family genes which involve in auxin metabolism. Moreover, ourfurther analyses showed that the IAA content in rice root obviously decreased inJMJ714-overexpressing lines, but increased in JMJ714-RNAi lines. In conclusion, our results implied that JMJ714might participate in the process of rice rootdevelopment by regulating the expression of auxin metabolism related genes and the IAA content in riceroot.