Changes in gene expression under water stress in the flag leaf and seed head during the grain-filling stage of two spring wheat cultivars

Abstract

Drought poses severe limitations on crop production. Therefore, drought tolerance mechanisms need to be better understood to select, modify and recommend certain cultivars of wheat. The grain filling stage of wheat development is particularly sensitive to water stress conditions. This research studied biological response to water stress under, well-watered (WW- 220 ml), moderate stress (MS- 110 ml), and severe stress (SS- 55 ml) conditions, with cultivars of soft white spring wheat (Alpowa and Idaho) during the early grain-filling stage of wheat development (Feekes 11.2) and under two duration of stress treatments (5, and 8 days), with a particular focus on the flag leaf and seed head. The flag leaf weights averaged across durations were 91%, 62% and 68%, 41% of well-watered under MS and SS in Alpowa and Idaho, respectively, compared with the well-watered control. The differential expressed genes were 2.32 and 3.9 fold more up and down-regulated genes in Alpowa compared to Idaho, respectively. Shared transcripts between stress intensities MS and SS constituted only 3 to 17% of the overall differentially expressed transcripts in both cultivars. Most of the top GO terms were predominantly down-regulated with a ratio of less than 1.0 under both stress intensities. The most abundant GO terms are related to transcriptional biological processes and to a lesser extent metabolic, transport, and translational activities. Seed head weights did not differ statistically among any of the water limitations treatments, cultivars, or durations. Idaho had 5.5 times the number of DE transcripts compared to Alpowa (338 in Alpowa, and 1843 in Idaho) with only 53 transcripts shared between the two cultivars in their response to water stress. The top GO terms for the biological process was predominantly downregulated especially in Idaho under both conditions (MS and SS) while in Alpowa a moderate tendency towards down-regulation was detected. The top twenty up and downregulated transcripts were examined for flag leaf and seed head.