Molecular Genetic Mechanisms of Heterosis in Sugarcane Cultivars Using a Comparative Transcriptome Analysis of Hybrids and Ancestral Parents

Abstract

Modern sugarcane cultivars (Saccharum spp. hybrids) are the major contributors to sucrose and bioenergy in the world. The global changes in gene expression and the molecular mechanism of heterosis between modern sugarcane hybrids and their parents remain to be elucidated. In this study, we performed a comparative transcriptome analysis between hybrids and their parents using the Illumina RNA-Seq method to understand the differences in transcript expression after hybridization. The results show that (1) introduction of the S. spontaneum lineage resulted in significant upregulation of biotic and abiotic stress resistance genes in S. hybrids, including hexokinase (HXK) genes, pathogenesis-related protein (PR1) genes, coronatine-insensitive protein (COI-1), jasmonate ZIM domain-containing protein (JAZ) genes, and serine/threonine protein kinase 2 (SnRK2) genes. (2) Transgressive genes in hybrids were mainly concentrated in the synthesis pathways of biotin and vitamin B6, helping establish advantages in terms of stress resistance, antioxidant activity, and growth. (3) Glutathione-S-transferase (GST) was likely to enhance stress resistance in hybrids, and corresponding genes were key positive selection genes in processes, including round-robin selection and other adaptations. In this study, we propose explanations for heterosis in sugarcane hybrids from a transcriptomic perspective, in addition to identifying candidate genes to aid in the improvement of sugarcane cultivars.