Comparative Transcriptome Analysis Revealed the Freezing Tolerance Signaling Events in Winter Rapeseed (Brassica rapa L.)

Abstract

Winter rapeseed (Brassica rapa L.) is an important oilseed crop in northwest China. Freezing stress severely limits its production and geographical distribution, and frequent extreme freezing events caused by climate change are increasing the chances of winter freeze-injury. However, the underlying mechanism of B. rapa response to freezing stress remains elusive. Here, B. rapa genome (v3.0) was used as a reference for the comparative transcriptomic analysis of Longyou 6 and Tianyou 2 (strong and weak cold tolerance, respectively) under different freezing stress. Before and after freezing stress, 5,982 and 11,630 unique differentially expressed genes (DEGs) between two cultivars were identified, respectively. After freezing stress, the GO terms in Tianyou 2 were mainly involved in “macromolecule biosynthetic process”, and those in Longyou 6 were involved in “response to stimulus” and “oxidoreductase activity”. Morphological and physiological results indicated that Longyou 6 retained a higher basal freezing resistance than Tinayou 2, and that cold acclimation could strengthen the basal freezing resistance. Freezing stress could activate the MAPK signal cascades, and the phosphorylation level of Longyou 6 showed a higher increase in response to freezing treatment than Tianyou 2. Based on our findings, it was speculated that the cell membrane of B. rapa perceives external signals under freezing stress, which are then transmitted to the nucleus through the cold-activated MAPK cascades and Ca2+-related protein kinase pathway, thus leading to activation of downstream target genes to enhance the freezing resistance of B. rapa.

Exogenous application of salicylic acid improves freezing stress tolerance in alfalfa

“…found that all pathways, except for the MAPK signaling pathway-plant that is predominant in alfalfa, confer freezing stress ( Song et al., 2016 ; Wang et al., 2021 ). The MAPK signaling pathway has been reported as important in freezing signal transduction in many plants ( Cowan and Storey, 2003 ; Liu and Zhou, 2018 ; Wu et al., 2022 ), which means it could have a similar function in our study. As for SA application, the domain KEGG pathways were fatty acid elongation, biosynthesis of secondary metabolites, biosynthesis of amino acids, metabolic pathway, and MAPK signaling pathway-plant.…”

How Antioxidants, Osmoregulation, Genes and Metabolites Regulate the Late Seeding Tolerance of Rapeseeds (Brassica napus L.) during Wintering

“…Meanwhile, with the more frequent occurrence of extreme weather resulting from global climate change, the requirements of rapeseed's stress resistance have been greatly raised, especially when wintering. According to reports, cold stress includes chilling (0-15 • C) and freezing stress (<0 • C) [38], and the rapeseed in our study encountered an extremely long chilling stress period from 28 November 2022, to 8 February 2023 (Figure 1D). The seed germination and seedling emergence stages of rapeseed are the most sensitive to abiotic or biotic stress, which directly determines a rapeseed population's density and grain yield [39].…”

Improved Cold Tolerance in <i>Brassica rapa</i>: Functional Diversification of BrICE1 and BrICE2 Paralogs via CBF and ROS Scavenging Pathways, Balancing Growth and Defense

“…Our previous studies have revealed that ROS accumulation and response speed are critical for freezing tolerance in B. rapa [31,38]. To further explore the relationship between BrICE1 and BrICE2 involvement in low-temperature resistance and ROS, we assayed ROS accumulation in BrICE1 and BrICE2 transgenic plants using nitroblue tetrazolium (NBT) histochemical staining after chilling (at 4 ℃ for 3 or 6 h) or freezing treatment (at -4 ℃ for 3 or 6 h).…”

“…Arabidopsis thaliana ecotype Col-0 and transgenic seedlings used in this study were grown on half-strength MS medium supplemented with 1% sucrose and 0.8% agar at 22 ℃ under a 16-h light/8h dark photoperiod. For soil growth, Arabidopsis and B. rapa seeds were vernalized at 4 ℃ for 3 d and then grown at 22 ℃ in a greenhouse under a 16-h light/8-h dark cycle condition [31,38].…”