Integrated endogenous hormones and transcriptome analysis contribute to fruit development related gene mining in Eriobotrya japonica.

Loquat has both a delicious taste and natural medicinal effects. Fruit yield is the foundation of loquat production. However, as loquat fruits ripen, the time course changes in endogenous hormones and the transcriptome are still unclear, and the mining of loquat fruit development-related genes is still limited. Pulps from four stages of fruit development, including 70 days after full-blooming (DAF) (Z01), 90 DAF (Z02), 110 DAF (Z03), and 130 DAF (Z04), were collected to detect the contents of endogenous hormones and conduct transcriptome analysis. The results revealed that the pulps thickened continuously at a steady speed, whereas the rapid fruit expansion before the Z02 stage could be attributed to a sharp expansion of seeds. In addition, the endogenous hormone levels of the pulps tended to differ among these four stages. A total of 39,051 genes were obtained, and each sample was compared. Z01-VS-Z02, Z01-VS-Z03, and Z01-VS-Z04 presented 2611, 12,594, and 19,214 differentially expressed genes (DEGs), respectively. We found that there were 259, 49, 47, 70, 169, 47, 22 and 33 DEGs related to Aux, GA, CTK, ABA, Eth, BR, SA and JA, respectively. GO and KEGG enrichment analyses revealed that the most obviously enriched terms were photosynthesis-antenna proteins, starch and sucrose metabolism, and photosynthesis. Cluster analysis of the expression trends of the DEGs revealed that 25 clusters were obtained, 16 of which were highly correlated with 1 to 5 hormones. A total of 25 and 28 core genes were systematically identified from clusters 21 and 25, respectively. Heterologous expression revealed that EjHsc70, a selected core gene, promoted Arabidopsis growth and could be involved in the development process of loquat fruit. This study provides new insights into fruit development in Eriobotrya japonica.