RNA-Seq Highlights Molecular Events Associated With Impaired Pollen-Pistil Interactions Following Short-Term Heat Stress in Brassica napus

Abstract

The global climate change is leading to increased frequency of heatwaves with crops getting exposed to extreme temperature events. Such temperature spikes during the reproductive stage of plant development can harm crop fertility and productivity. Here we report the response of short-term heat stress events on the pollen and pistil tissues in a commercially grown cultivar of Brassica napus. Our data reveals that short-term temperature spikes not only affect pollen fitness but also impair the ability of the pistil to support pollen germination and pollen tube growth and that the heat stress sensitivity of pistil can have severe consequences for seed set and yield. Comparative transcriptome profiling of non-stressed and heat-stressed (40°C for 30 min) pollen and pistil (stigma + style) highlighted the underlying cellular mechanisms involved in heat stress response in these reproductive tissues. In pollen, cell wall organization and cellular transport-related genes possibly regulate pollen fitness under heat stress while the heat stress-induced repression of transcription factor encoding transcripts is a feature of the pistil response. Overall, high temperature altered the expression of genes involved in protein processing, regulation of transcription, pollen-pistil interactions, and misregulation of cellular organization, transport, and metabolism. Our results show that short episodes of high-temperature exposure in B. napus modulate key regulatory pathways disrupted reproductive processes, ultimately translating to yield loss. Further investigations on the genes and networks identified in the present study pave a way toward genetic improvement of the thermotolerance and reproductive performance of B. napus varieties.

Genomic Signatures of Sexual Selection on Pollen-Expressed Genes in Arabis alpina

“…We further tested how sensitive our results were to our reliance on expression data from A. thaliana to identify pollen-expressed genes. As no similarly detailed or replicated expression resource was available for A. alpina or other Brassicaceae species, we identified pollen- and unpollinated pistil-expressed genes based on publicly available data from Brassica napus (Lohani et al 2021) and A. thaliana (see Materials and Methods and Supplementary Note 1 for details). We inferred the DFE of the A. alpina orthologs of these gene sets and inferred stronger purifying selection on pollen than on pistil-expressed genes in the Gre2 population, both based on B. napus and A. thaliana data (0 < N e s < 1 estimates based on A. thaliana expression data= pollen: 13.67±0.14%, pistil: 15.56±0.10%; B. napus = pollen: 12.03±0.17%, pistil: 13.97±0.09%).…”

“…thaliana to identify pollen-expressed genes. As no similarly detailed or replicated expression resource was available for A. alpina or other Brassicaceae species, we identified pollen-and unpollinated pistil-expressed genes based on publicly available data from Brassica napus (Lohani et al 2021) Our results suggest that despite differences in the ubiquity and abundance of genes expressed, vegetative pollen cell and sperm-expressed genes show contrasting patterns of purifying selection, with vegetative pollen-expressed genes consistently showing a lower proportion of effectively neutral sites. In contrast, gene expression breadth seems to affect the differences in adaptive evolution between vegetative pollen and sperm.…”

The Role of Endoplasmic Reticulum Stress Response in Pollen Development and Heat Stress Tolerance

“…This vulnerability at the reproductive stage leads to a significant reduction in seed set and crop yields. The pollen development and pollination are particularly vulnerable to heat stress events as elevated temperatures during pollen development can trigger pollen abortion (Reiu et al, 2017;Begcy et al, 2019;Lohani et al, 2020Lohani et al, , 2021. Recent investigations have uncovered the crucial role of the UPR for ensuring normal pollen development and successful fertilization (Deng et al, 2013(Deng et al, , 2016Fragkostefanakis et al, 2016).…”

Circular RNAs Repertoire and Expression Profile during Brassica rapa Pollen Development

“…Tubes were then centrifuged at 4 • C for 3 min at 150 g, and the supernatant was discarded. The pellet was washed with modified half strength B5 medium, and finally, pure pollen grains were collected from the medium using centrifugation at 4 • C for 3 min at 150 g. After discarding the medium, the pellet was immediately frozen in liquid nitrogen and stored at −80 • C for later use [31].…”