Walnut -Acetylserotonin Methyltransferase Gene Family Genome-Wide Identification and Diverse Functions Characterization During Flower Bud Development.

Melatonin widely mediates multiple developmental dynamics in plants as a vital growth stimulator, stress protector, and developmental regulator. -acetylserotonin methyltransferase (ASMT) is the key enzyme that catalyzes the final step of melatonin biosynthesis in plants and plays an essential role in the plant melatonin regulatory network. Studies of ASMT have contributed to understanding the mechanism of melatonin biosynthesis in plants. However, gene is currently uncharacterized in most plants. In this study, we characterized the gene family using bioinformatics in a melatonin-rich plant, walnut. Phylogenetic, gene structure, conserved motifs, promoter elements, interacting proteins and miRNA analyses were also performed. The expansion and differentiation of the ASMT family occurred before the onset of the plant terrestrialization. genes were more differentiated in dicotyledonous plants. Forty-six genes were distributed in clusters on 10 chromosomes of walnut. Four genes had homologous relationships both within walnut and between species. -regulatory elements showed that was mainly induced by light and hormones, and targeted cleavage of miRNA172 and miR399 may be an important pathway to suppress expression. Transcriptome data showed that 13 were differentially expressed at different periods of walnut bud development. WGCNA showed that were coexpressed with genes regulating cell fate and epigenetic modifications during early physiological differentiation of walnut female flower buds. were highly expressed during morphological differentiation of flower buds, associated with altered stress capacity of walnut flower buds, and predicted to be involved in the regulatory network of abscisic acid, salicylic acid, and cytokinin in walnut. The qRT-PCR validated the results of differential expression analysis and further provided three genes with different expression profiles in walnut flower bud development. Our study explored the evolutionary relationships of the plant gene family and the functional characteristics of walnut . It provides a valuable perspective for further understanding the complex melatonin mechanisms in plant developmental regulation.