Transcriptome and translatome changes in germinated pollen under heat stress uncover roles of transporter genes involved in pollen tube growth

Abstract

Plant reproduction is one key biological process very sensitive to heat stress and, as a consequence, enhanced global warming poses serious threats to food security worldwide. In this work we have used a high-resolution ribosome profiling technology to study how heat affects both the transcriptome and the translatome of Arabidopsis thaliana pollen germinated in vitro. Overall, a high correlation between transcriptional and translational responses to high temperature was found, but specific regulations at the translational level were also present. We show that bona fide heat shock genes are induced by high temperature indicating that in vitro germinated pollen is a suitable system to understand the molecular basis of heat responses. Concurrently heat induced significant downregulation of key membrane transporters required for pollen tube growth, thus uncovering heatsensitive targets. We also found that a large subset of the heat-repressed transporters is specifically up-regulated, in a coordinated manner, with canonical heat-shock genes in pollen tubes grown in vitro and semi in vivo, based on published transcriptomes from Arabidopsis thaliana. Ribosome footprints were also detected in gene sequences annotated as non-coding, highlighting the potential for novel translatable genes and translational dynamics.

Heat-Induced Oxidation of the Nuclei and Cytosol

“…In turn, HSFs stimulate the expression of HSP chaperones and ROS-processing proteins and antioxidant-related transcription factors such as ZAT10 and HSFA1D, which stimulates the APX2 expression. The HS-induced changes in the transcriptome profile reported here are similar to previous reports, with the increase in transcripts encoding HSPs and significant downregulation of membrane proteins such as transporters ( Poidevin et al, 2020 ).…”

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

“…Similarly, chx21/23 double mutant display male-sterility as the pollen tube is incapable of reaching the ovules ( Lu et al, 2011 ). There is a recent report of the downregulation of these transporters in in vitro germinated Arabidopsis pollen exposed to heat stress ( Poidevin et al, 2020 ). Sucrose transport gene AtSUC1 shows high expression in pollen.…”

Characterization of novel pollen-expressed transcripts reveals their potential roles in pollen heat stress response inArabidopsis thaliana

“…Sequence pairs were trimmed and filtered using Trimmomatic v. 032 (31). After filtering sequences to remove multiplexing barcodes and sequencing adapters using NGS QC Toolkit The bioinformatics protocols for the GP_HS libraries followed the same procedures as described (35) with a few changes. First, during the cleaning steps the non-coding RNAs were not bioinformatically removed.…”

“…We interrogated yet another pollen RNAseq dataset from an HS experiment in which pollen was germinated in vitro for 5 hours at 24°C or 35°C for 5 hours (GP_HS dataset; (35)).…”

“…Ribosome profiling, also known as ribosome sequencing (Riboseq), is a powerful method for identifying transcripts engaged with ribosomes and allows for the likelihood prediction of transcripts undergoing in vivo translation. Parallel to the RNAseq of the GP_HS experiment, sequencing of ribosome protected fragments (RPF) was performed from the same in vitro HS experiment of in vitro germinated pollen (35). As the germinated pollen sequencing libraries are strand-oriented, we determined the coding strand for each of these XLOC genes (Table S6).…”