2018 ASHS Annual Conference

In tree fruit, somatic mutations may alter fruit color, size, shape, and maturation date. ‘Autumn Gala’ is a somatic mutation from a widely grown apple cultivar ‘Gala’. The fruit of ‘Autumn Gala’ distinguish from those of ‘Gala’ by a 4-week delayed maturation date and a longer shelf life. Fruit maturation is a genetically programmed event involving numerous biochemical, physiological, and structural alterations. To understand the molecular mechanisms underlying the remarkable fruit maturation delay and shelf life extension, RNA-sequencing (RNA-Seq) analyses were conducted at various stages during fruit development and postharvest storage from ‘Gala’ and ‘Autumn Gala’. A total of 102 RNA-Seq libraries, including 48 (24x2) for ‘Gala’ and 54 (27x2) for ‘Autumn Gala’ were sequenced using next-generation genome sequencer illumina HiSeq 2500. RNA-Seq data analysis was conducted using CLC Genomics Workbench and the software package R. To identify casual factors responsible for late maturation, gene expression profiles throughout the developmental stages were analyzed. In total 9,368 differentially expressed genes (DEGs) were identified between ‘Gala’ and ‘Autumn Gala’ at each developmental stages and between the adjacent stages. A weighted gene co-expression network analysis (WGCNA) of the DEGs uncovered a network module of 57 genes highly correlated (r=0.98, P=4e-21) with the suppressed expression in ‘Autumn Gala’. Among the 57 genes, 49 were located within a 2.7Mb region on chromosome 6. Further analysis is underway to identify if there are any genomic structural changes in this region that might have impacted on fruit maturation.