Abstract

Functional genomics for Delineating Molecular Regulatory Mechanism of Dormancy Release in Apple (Malus domestica Borkh.)

Anil Singh, Senior Scientist, Indian Institute of Agricultural Biotechnology

Chilling availability during winter dormancy plays an important role in the phenological events in apple. Insufficient accumulation of chilling leads to inevitable physiological symptoms which adversely affect the yield and quality of the fruit. Due to climate change in recent decades, decreasing trend in available chilling has been observed in apple growing regions of Himachal Pradesh, India. Thus, understanding the molecular mechanism of chilling-mediated dormancy release in apple is crucial. The comparative transcriptome analysis for dormancy release and fruit set under differential chilling conditions showed differential expression of genes related to phytohormones metabolism, including ABA, GA, auxin, ethylene and cytokinin; and floral time regulation, including DAM, FLC-like, FT-like and TF1-like genes. The co-expression network analysis identified two high chill specific gene modules along with their hub genes, enriched for GO term “post-embryonic development” which might be involved in the regulation of meristematic activity during dormancy release. In addition, the differential expression of genes encoding DNA methyltransferases and DNA glycosylases was also observed. Therefore, the genomic DNA methylation status was analyzed using methylation sensitive amplified polymorphism (MSAP). The methylation pattern suggested that high chilling availability during dormancy period was associated with reduction in cytosine methylation along the dormancy release and fruit set in apple. Members of MADS-box gene family are known to regulate diverse physiological processes including dormancy and flowering time in various plants. The characterization of 142 identified apple MADS-box genes was performed. The identification of six DAM and four FLC-like genes, and their expression analysis with some other genes (FRI, FT, LFY, SOC1 and CO) leads to hypothetical model of regulating dormancy release and flower time in apple. In addition, using computational approaches, the funct