Comparative Transcriptome Analysis of High- and Low- Embryogenic Hevea brasiliensis Genotypes Reveals Involvement of Phytohormones in Somatic Embryogenesis

AbstractBackground Rubber plant (Hevea brasiliensis) is one of the major sources of latex. Somatic embryogenesis (SE) is a promising alterative to its propagation by grafting and seed. Phytohormones have been shown to influence SE in different plant species. However, limited knowledge is available on the role of phytohormones in SE inHevea. The anther cultures of twoHeveagenotypes (Yunyan 73477-YT) and Reken 628-RT) with contrasting SE rate were established and four stages i.e., anthers (h), anther induced callus (y), callus differentiation state (f), and somatic embryos (p) were studied. UPLC-ESI-MS/MS and transcriptome analyses were used to study phytohormone accumulation and related expression changes in biosynthesis and signaling genes. Results YT showed higher callus induction rate than RT. Of the two genotypes, only YT exhibited successful SE. We detected auxins, cytokinins (CKs), abscisic acid (ABA), jasmonic acid (JA), salicylic acid (SA), gibberellins (GAs), and ethylene (ETH) in the two genotypes. Indole-3-acetic acid (IAA), CKs, ABA, and ETH had notable differences in the studied stages of the two genotypes. The DEGs identified in treatment comparisons were majorly enriched in MAPK and phytohormone signaling, biosynthesis of secondary metabolites, and metabolic pathways. The expression changes in IAA, CK, ABA, and ETH biosynthesis and singling genes confirmed the differential accumulation of respective phytohormones in the two genotypes. Conclusion These results suggest potential roles of phytohormones in SE inHevea.