Abstract
Water deficiencies are one of the most serious challenges to crop productivity. To improve our understanding of soil moisture stress, we performed RNA-Seq analysis using roots from 4-week-old rice seedlings grown in soil that had been subjected to drought conditions for 2–3 d. In all, 1,098 genes were up-regulated in response to soil moisture stress for 3 d, which causes severe damage in root development after recovery, unlikely that of 2 d. Comparison with previous transcriptome data produced in drought condition indicated that more than 68% of our candidate genes were not previously identified, emphasizing the novelty of our transcriptome analysis for drought response in soil condition. We then validated the expression patterns of two candidate genes using a promoter-GUS reporter system in planta and monitored the stress response with novel molecular markers. An integrating omics tool, MapMan analysis, indicated that RING box E3 ligases in the ubiquitin-proteasome pathways are significantly stimulated by induced drought. We also analyzed the functions of 66 candidate genes that have been functionally investigated previously, suggesting the primary roles of our candidate genes in resistance or tolerance relating traits including drought tolerance (29 genes) through literature searches besides diverse regulatory roles of our candidate genes for morphological traits (15 genes) or physiological traits (22 genes). Of these, we used a T-DNA insertional mutant of rice phytochrome B (OsPhyB) that negatively regulates a plant's degree of tolerance to water deficiencies through the control of total leaf area and stomatal density based on previous finding. Unlike previous result, we found that OsPhyB represses the activity of ascorbate peroxidase and catalase mediating reactive oxygen species (ROS) processing machinery required for drought tolerance of roots in soil condition, suggesting the potential significance of remaining uncharacterized candidate genes for manipulating drought tolerance in rice.
Highlights
Water deficiencies at critical growth stages can seriously restrict crop productivity
The expression patterns were examined for two genes that had been identified as molecular markers of the drought-stress response, i.e., OsDREB2b (LOC_Os05g27930) and OsbZIP23 (LOC_Os02g52780) (Xiang et al, 2008; Matsukura et al, 2010)
We identified that dry weight after recovery of root samples exposed to water deficiency treatment (WD) stress for 2 d increased, whereas that of root samples exposed to WD stress for 3 d decreased and the rice plants were mostly died due to the damage augmented by the stress (Figures 2F–J)
Summary
Water deficiencies at critical growth stages can seriously restrict crop productivity. Functions of 97 genes were introduced (Yamamoto et al, 2012). Stomatal conductance is one of the major mechanisms for conferring the drought tolerance in vegetative organs and functions of at least eight genes are related to this mechanism. Calmodulin-like (CML) genes are known to regulate plant responses to abiotic stresses including drought. Transgenic plants over-expressing OsCML4 gene confer drought tolerance through ROS-scavenging process (Yin et al, 2015). ABA responsive AP2-like gene 1 (ARAG1) is related to drought tolerance during seedling stage and ABA sensitivity during germination (Zhao et al, 2010). Functions of a few genes have been reported in the association with both drought stress and root development. Root-driven drought tolerance is more effective for current and future applications but our knowledge on this process is still limited
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
