Lignin de ciency in the endocarp of walnuts causes nuts exposed, lead a inconvenience in processing and transportation of walnuts, and easy to produce insect damage, mildew, affecting the quality of walnuts. Cinnamyl alcohol dehydrogenase (CAD) is the nal enzyme in the phenylpropanoid metabolic pathway in lignin, converting cinnamaldehyde to cinnamyl alcohol and catalyzing the synthesis of lignin monomers. To investigate the lignin metabolism pathway in walnut, the JrCAD genes were characterized. In this study, all 18 JrCADs were identi ed and phylogenetic relationships, gene structure, protein motifs, collinearity and expression pattern of the JrCADs were also analyzed. All JrCADs could be divided into three groups based on phylogenetic tree. Transcriptome data demonstrated that JrCADs have different expression patterns in walnut endocarp at development stages. Combined with qRT-PCR data, we nally identi ed several candidate JrCADs that involved in the process of endocarp sclerosis. These results provide valuable candidate genes for dissecting the functions and molecular mechanisms of lignin accumulation in walnut.

Lignin deficiency in the endocarp of walnuts causes nuts exposed, lead a inconvenience in processing and transportation of walnuts, and easy to produce insect damage, mildew, affecting the quality of walnuts. Cinnamyl alcohol dehydrogenase (CAD) is the final enzyme in the phenylpropanoid metabolic pathway in lignin, converting cinnamaldehyde to cinnamyl alcohol and catalyzing the synthesis of lignin monomers. To investigate the lignin metabolism pathway in walnut, the JrCAD genes were characterized. In this study, all 18 JrCADs were identified and phylogenetic relationships, gene structure, protein motifs, collinearity and expression pattern of the JrCADs were also analyzed. All JrCADs could be divided into three groups based on phylogenetic tree. Transcriptome data demonstrated that JrCADs have different expression patterns in walnut endocarp at development stages. Combined with qRT-PCR data, we finally identified several candidate JrCADs that involved in the process of endocarp sclerosis. These results provide valuable candidate genes for dissecting the functions and molecular mechanisms of lignin accumulation in walnut.

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