In-Depth Proteomic Analysis of the Secondary Dormancy Induction by Hypoxia or High Temperature in Barley Grains

In barley, incubation of primary dormant (D1) grains on water under conditions that do not allow germination, i.e. 30 degrees C in air and 15 degrees C or 30 degrees C in 5% O-2, induces a secondary dormancy (D2) expressed as a loss of the ability to germinate at 15 degrees C in air. The aim of this study was to compare the proteome of barley embryos isolated from D1 grains and D2 ones after induction of D2 at 30 degrees C or in hypoxia at 15 degrees C or 30 degrees C. Total soluble proteins were analyzed by 2DE gel-based proteomics, allowing the selection of 130 differentially accumulated proteins (DAPs) among 1,575 detected spots. According to the protein abundance profiles, the DAPs were grouped into six abundance-based similarity clusters. Induction of D2 is mainly characterized by a down-accumulation of proteins belonging to cluster 3 (storage proteins, proteases, alpha-amylase inhibitors and histone deacetylase HD2) and an up-accumulation of proteins belonging to cluster 4 (1-Cys peroxiredoxin, lipoxygenase2 and caleosin). The correlation-based network analysis for each cluster highlighted central protein hub. In addition, most of genes encoding DAPs display high co-expression degree with 19 transcription factors. Finally, this work points out that similar molecular events accompany the modulation of dormancy cycling by both temperature and oxygen, including post-translational, transcriptional and epigenetic regulation.

Automated summary

This study compares the proteome of barley embryos induced to secondary dormancy (D2) under different temperature and hypoxia conditions. The results indicate that D2 induction is mainly associated with changes in protein accumulation and co-expression of genes. These findings suggest that temperature and oxygen have similar molecular regulatory mechanisms in dormancy cycling.