Abstract
Wheat grains are an important source of human food but current production amounts cannot meet world needs. Environmental conditions such as high temperature (above 30°C) could affect wheat production negatively. Plants from two wheat genotypes have been subjected to two growth temperature regimes. One set has been grown at an optimum daily mean temperature of 19°C while the second set of plants has been subjected to warming at 27°C from two to 13 days after anthesis (daa). While warming did not affect mean grain number per spike, it significantly reduced other yield-related indicators such as grain width, length, volume and maximal cell numbers in the endosperm. Whole genome expression analysis identified 6,258 and 5,220 genes, respectively, whose expression was affected by temperature in the two genotypes. Co-expression analysis using WGCNA (Weighted Gene Coexpression Network Analysis) uncovered modules (groups of co-expressed genes) associated with agronomic traits. In particular, modules enriched in genes related to nutrient reservoir and endopeptidase inhibitor activities were found to be positively associated with cell numbers in the endosperm. A hypothetical model pertaining to the effects of warming on gene expression and growth in wheat grain is proposed. Under moderately high temperature conditions, network analyses suggest a negative effect of the expression of genes related to seed storage proteins and starch biosynthesis on the grain size in wheat.
Highlights
While the two genotypes differed in terms of numerical results, they behaved in such a similar way that the same conclusions and comments could be drawn
The main results for the genotype SxB49 will be given in different sections as supplemental data
We found that the maximum filling rate (2.74 vs 2.68 mg dry matter per daa) is not affected by temperature
Summary
The dry mass of an individual grain increases slowly and the enlargement of the grain structure results mainly from the rapid influx of water into the endosperm This phase is complete within about 15 daa depending on the wheat genotype and the environment. Qin et al [30] identified a total of 6,560 probe sets that displayed changes in expression after heat treatment at 40 ̊C with or without acclimatation at 34 ̊C This set included HSPs, HSFs, and gene encoding proteins involved in phytohormone biosynthesis/ signaling, calcium, sugar signal pathways, RNA metabolism, ribosomal proteins, as well as primary and secondary metabolisms. The subsequent effect of these events is a net reduction in grain yield
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