Cloning and Expression Analysis of JrMYB44 and JrMYB13 Genes in Endocarp of'Xinlu'Walnut
Lignin synthesis is indispensible for endocarp sclerosis in walnut;however,its regulatory mechanism remains elusive.In this study,we successfully cloned the coding sequences(CDS)of two lignin synthesis-related genes,JrMYB44 and JrMYB13,which were closely associated with lignin synthesis in walnut.We conducted comprehensive analysis to determin the expression levels of these genes in different tissues and organs of walnut,as well as in both sclerotized and non-sclerotized parts of the endocarp during different developmental stages,and we also investigated the subcellular locali-zation of these two proteins.The results showed that:JrMYB44 and JrMYB13 encoded 319 and 317 amino acids,respectively,and the two proteins showed a homologous of 39.5％.Phylogenetic tree analysis revealed that JrMYB44 was close to the homologous proteins of Juglans regia × Juglans major hybrid walnut and pecan,while JrMYB13 was only close to the homologous proteins of Jug-lans regia × J uglans major hybrid walnut.Subcellular localization result showed that both JrMYB44 and JrMYB13 were expressed in the nucleus.Gene expression investigation revealed that the JrMYB44 gene was mainly expressed in the non-sclerotized zone of walnut endocarp,and its expres-sion level at different developmental stages of endocarp was negatively correlated with the lignin con-tent.Therefore,the JrMYB44 gene would play a negative role in lignin synthesis.By contrast,the JrMYB13 gene was mainly expressed in the sclerotized zone of walnut endocarp and its expression lev-el increased along with the increase of lignin content,indicating that the JrMYB13 gene might play a positive role in lignin synthesis.
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