Shoot Apex Differentiation on Freezing Resistance and its Regulatory Genes in the Wheat Seedling Stage

Abstract

Evaluating the biological mechanism of winter wheat in resisting freezing stress is important. The aim of this study was to clarify the effect of the shoot apex differentiation status on freezing resistance in wheat and identify regulatory genes. Nongda 5181 (ND5181) and its ethyl methanesulfonate (EMS)-mutated wheat lines were used as research materials. Three wheat varieties showed strong freezing resistance and slow shoot apex differentiation, whereas the other three wheat varieties showed weak freezing resistance and rapid shoot apex differentiation. The results showed that plants with faster shoot apex development differentiated into the double-ridge stage before overwintering, and the re-greening rate was lower than 50%. In contrast, wheat with slower shoot apex differentiation differentiated into the elongation or single-ridge stages, and the re-greening rate exceeded 90%. To identify the genes affecting wheat shoot apex differentiation, RNA sequencing (RNA-seq) was employed to analyse differentially expressed genes in ND5181 and M-8052 (with slower shoot apex differentiation). At the three-leaf stage, most of the ND5181 highly expressed genes were chlorophyll synthesis, protein synthesis-related and resistance genes, whereas those of M-8052 samples were histones and ribosomal proteins. After the three-leaf stage at 40 days, most of the highly expressed genes in ND5181 were related to energy metabolism, development and resistance, whereas those of M-8052 were protein synthesis-related genes or resistance genes.