Enhanced sugar accumulation and regulated plant hormone signalling genes contribute to cold tolerance in hypoploid Saccharum spontaneum

Hongli Yang,Xinghua Yu,Xianhong Wang,Tianju Wang,Chunfang Wang,Qinghui Yang,Yang Yang

doi:10.1186/s12864-020-06917-z

Abstract

BackgroundWild sugarcane Saccharum spontaneum plants vary in ploidy, which complicates the utilization of its germplasm in sugarcane breeding. Investigations on cold tolerance in relation to different ploidies in S. spontaneum may promote the exploitation of its germplasm and accelerate the improvement of sugarcane varieties.ResultsA hypoploid clone 12–23 (2n = 54) and hyperploid clone 15–28 (2n = 92) of S. spontaneum were analysed under cold stress from morphological, physiological, and transcriptomic perspectives. Compared with clone 15–28, clone 12–23 plants had lower plant height, leaf length, internode length, stem diameter, and leaf width; depressed stomata and prominent bristles and papillae; and thick leaves with higher bulliform cell groups and thicker adaxial epidermis. Compared with clone 15–28, clone 12–23 showed significantly lower electrical conductivity, significantly higher water content, soluble protein content, and superoxide dismutase activity, and significantly higher soluble sugar content and peroxidase activity. Under cold stress, the number of upregulated genes and downregulated genes of clone 12–23 was higher than clone 15–28, and many stress response genes and pathways were affected and enriched to varying degrees, particularly sugar and starch metabolic pathways and plant hormone signalling pathways. Under cold stress, the activity of 6-phosphate glucose trehalose synthase, trehalose phosphate phosphatase, and brassinosteroid-signalling kinase and the content of trehalose and brassinosteroids of clone 12–23 increased.ConclusionsCompared with hyperploid clone 15–28, hypoploid clone 12–23 maintained a more robust osmotic adjustment system through sugar accumulation and hormonal regulation, which resulted in stronger cold tolerance.

Highlights

Wild sugarcane Saccharum spontaneum plants vary in ploidy, which complicates the utilization of its germplasm in sugarcane breeding
Leaf anatomical analysis showed that the stomata of the 12–23 clone were depressed, and the bristles and papillae were prominent (Fig. 1d and d’), whereas the stomata of clone 15–28 were not depressed, and their bristles and papillae were fewer in number and not prominent (Fig. 1e and e’)
The results showed that the differential fold change in the expression of genes detected by Real-time fluorescent quantitative reverse transcription PCR (RT-qPCR) was different from that revealed by RNA-seq, but the trends of gene expression presented by the two methods were largely the same (Fig. 5b) (Additional file 4: Figure S1)

Summary

Introduction

Wild sugarcane Saccharum spontaneum plants vary in ploidy, which complicates the utilization of its germplasm in sugarcane breeding. Investigations on cold tolerance in relation to different ploidies in S. spontaneum may promote the exploitation of its germplasm and accelerate the improvement of sugarcane varieties. S. spontaneum belongs to the perennial herb of the family Gramineae and genus Saccharum, has both asexual and sexual reproductive abilities [3, 4], can grow in a variety of environments, such as drought, cold and high salt conditions [5], has varied phenotypes and strong adaptability, can provide rich genetic diversity for sugarcane breeding, and is the main source of desirable genes resistant to pests, diseases, cold, and drought [6, 7].

Methods

Results

Discussion

Conclusion