Abstract
Field pea (Pisum sativum L.), a cool-season legume crop, is known for poor heat tolerance. Our previous work identified PR11-2 and PR11-90 as heat tolerant and susceptible lines in a recombinant inbred population. CDC Amarillo, a Canadian elite pea variety, was considered as another heat tolerant variety based on its similar field performance as PR11-2. This study aimed to characterize the differential transcription. Plants of these three varieties were stressed for 3 h at 38°C prior to self-pollination, and RNAs from heat stressed anthers and stipules on the same flowering node were extracted and sequenced via the Illumina NovaSeq platform for the characterization of heat responsive genes. In silico results were further validated by qPCR assay. Differentially expressed genes (DEGs) were identified at log2 |fold change (FC)| ≥ 2 between high temperature and control temperature, the three varieties shared 588 DEGs which were up-regulated and 220 genes which were down-regulated in anthers when subjected to heat treatment. In stipules, 879 DEGs (463/416 upregulation/downregulation) were consistent among varieties. The above heat-induced genes of the two plant organs were related to several biological processes i.e., response to heat, protein folding and DNA templated transcription. Ten gene ontology (GO) terms were over-represented in the consistently down-regulated DEGs of the two organs, and these terms were mainly related to cell wall macromolecule metabolism, lipid transport, lipid localization, and lipid metabolic processes. GO enrichment analysis on distinct DEGs of individual pea varieties suggested that heat affected biological processes were dynamic, and variety distinct responses provide insight into molecular mechanisms of heat-tolerance response. Several biological processes, e.g., cellular response to DNA damage stimulus in stipule, electron transport chain in anther that were only observed in heat induced PR11-2 and CDC Amarillo, and their relevance to field pea heat tolerance is worth further validation.
Highlights
Human activities have contributed approximately 1 ̊C temperature increase globally since the Industrial Age, and are predicted to cause another 0.5–1 ̊C increase in the period between 2030 and 2052 according to current greenhouse gas emission rates [1]
To understand transcriptional reprogramming of field pea in response to Heat stress (HS), we performed deep RNA sequencing of stipule and anther organs subjected to 38 ̊C for 3 h among three varieties using the NovoSeq sequencing platform
The reads were mapped to the pea reference genome [37], and most reads were successfully aligned to the pea genome, which implies good quality of the deep sequencing
Summary
Human activities have contributed approximately 1 ̊C temperature increase globally since the Industrial Age, and are predicted to cause another 0.5–1 ̊C increase in the period between 2030 and 2052 according to current greenhouse gas emission rates [1]. In Canada, where its pea production accounts for one third of the global production, lowered grain yield was observed in summers when the maximum temperature exceeded 28 ̊C during flowering, or the seasonal temperature was over 17.5 ̊C [3, 4]. Because of the concern about a warming summer in North America, physiological studies on HS related damage on field pea, the reproductive plant parts, have been conducted in the last decade. A longer duration from sowing to flowering termination, and greater pod production per plant contributed to increased grain yield potential at both hot and normal conditions, and several stable quantitative trait loci were characterized related to flowering and yield component traits [4]. The authors further characterized putative genomic loci of heat responsive traits, e.g., canopy temperature, pod number and chlorophyll concentration, via a pea genome wide association mapping study [11]
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