Proteomic analysis reveals differentially abundant proteins involved in post-pollination responses to heat stress in Brassica napus

Heat stress significantly reduces canola seed production during the post-pollination stages. This study explored changes in the proteome of flowers on the main stem of three Brassica napus cultivars exposed to transient heat stress after pollination. Flowers at the 2nd to 5th reproductive nodes on the main stem were collected on days 0, 1, 3 and 6 of heat stress and control treatments. The three cultivars, Alku, AV-Ruby, and YM11, exhibited varying degrees of heat sensitivity and resilience based on seed production in pods at these reproductive nodes. The seed yield per pod under heat stress was 75.3 % of the control in Alku and 64.2 % in YM11. However, AV-Ruby retained 93.5 % of its seed yield under heat stress, from which we conclude AV-Ruby was more resilient to heat stress during the post-pollination stage than Alku or YM11. There were 474 differentially abundant proteins (DAPs) identified across all cultivars and time points. Among the DAPs, two HSP20-like chaperones (A0A078I8F7, A0A078JBL3) and one HSP-related protein (A0A078JJT8) were consistently highly abundant under heat and were strong candidates as heat responsive proteins. Pathways related to maintaining membrane integrity were specifically enriched in AV-Ruby, and deserve further study for their potential involvement in heat tolerance. SIGNIFICANCE OF THE STUDY: Heat stress is a major factor threatening seed yield in cool season crops including oilseed rape, particularly during the post-pollination stages when pollination, fertilization, and embryo development are highly vulnerable to elevated temperatures. A comparative proteomic analysis was carried out to identify heat-responsive proteins during the post-pollination period. Among the DAPs, three were consistently associated with heat stress response. A range of biological processes, including protein folding and stress signalling, were involved in a general response to heat stress in all cultivars. Furthermore, pathways related to maintaining membrane integrity were specifically enhanced in a heat-resilient cultivar. These findings provide new insights into the heat response at the protein level and lay the groundwork for identifying potential molecular targets for breeding heat-tolerant oilseed rape cultivars.