Comparative physiology and transcriptome analysis reveals the regulatory mechanism of genome duplication enhancing cold resistance in Fragaria nilgerrensis

Abstract

Polyploidization plays an important role in plant adaption to adverse environments, but the mechanism by which polyploidization confers adaptation to cold stress remains elusive. Here, autotetraploid strawberry (2n = 4x = 28) was successfully synthesized from wild strawberry (Fragaria nilgerrensis; 2n = 2x = 14) using a primary meristem processing technique. The autotetraploid plants exhibited a higher resistance to cold stress compared to their parental diploids, revealed by a series of physiological-biochemical examinations. Transcriptome analysis showed that expression pattern changes of genes in several pathways were the key contributors to the high cold resistance of autotetraploid strawberry. These main players included Ca2+ signal transduction, transcription factors (TFs), reactive oxygen species (ROS) scavenging enzyme, phenylpropanoid biosynthesis, abscisic acid (ABA) signaling and carbohydrate metabolism. The coordinate action of these factors enhanced the antioxidant defense system and protected the integrity of membranes and cellular organelles. Notably, gene co-expression network analysis (WGCNA) demonstrated that four hub genes (regulating cinnamyl-alcohol dehydrogenase (CAD), peroxidase (POD), caffeoyl-CoA O-methyltransferase (CCoAMT) and calmodulin-like protein (CML)) function much importantly in the network regulating this high cold resistance. Therefore, a model is proposed to elucidate the regulatory mechanisms of high cold resistance in the autotetraploid strawberry. The present findings provide new insights into understanding the complex regulatory network responsible for enhancing cold resistance in ployploid plants.