Drought response in the spikes of barley: gene expression in the lemma, palea, awn, and seed

Abstract

The photosynthetic organs of the barley spike (lemma, palea, and awn) are considered resistant to drought. However, there is little information about gene expression in the spike organs under drought conditions. We compared response of the transcriptome of the lemma, palea, awn, and seed to drought stress using the Barley1 Genome Array. Barley plants were exposed to drought treatment for 4 days at the grain-filling stage by withholding water. At the end of the stress, relative water content of the lemma, palea, and awn dropped from 85% to 60%. Nevertheless, the water content of the seed only decreased from 89% to 81%. Transcript abundance followed the water status of the spike organs; the awn had more drought-regulated genes followed by lemma and palea, and the seed showed very little change in gene expression. Despite expressing more drought-associated genes, many genes for amino acid, amino acid derivative, and carbohydrate metabolism, as well as for photosynthesis, respiration, and stress response, were down-regulated in the awn compared with the lemma, palea, and seed. This suggests that the lemma and the palea are more resistant to drought stress compared with the awn.

An-1 Encodes a Basic Helix-Loop-Helix Protein That Regulates Awn Development, Grain Size, and Grain Number in Rice

“…In contrast with long awns increasing yield in barley and wheat (Abebe et al, 2010), long-awn formation reduced yield per plant in rice, which might partly explain why the long awn trait was under strong artificial selection during rice domestication. Tajima purifying selection (Tajima, 1989).…”

“…However, long awns are not favorable during harvest and storage; hence, this trait was artificially selected during domestication. Even so, long awns are retained in some cereal crops, such as wheat and barley, because long awns contribute significantly to photosynthesis and yield (Abebe et al, 2010). On the contrary, most cultivated rice bear no awns or very short awns because the round rice awn contains only one vascular bundle and may not contribute to photosynthesis (Toriba et al, 2010).…”

Drought Stress Tolerance Mechanisms in Barley and Its Relevance to Cereals

“…Some of the examples related to identification of key genes using transcriptome analysis have been used to create transgenic plants and validated under field conditions, which include a stress-responsive NAC transcription factor (SNAC1) (Hu et al 2006) and late embryogenesis abundant (LEA) genes in rice (Xiao et al 2007). In barley, a transcriptomic approach has been employed to study spike responses to light and drought stresses (Abebe et al 2010;Mangelsen et al 2010), as well as near isogenic lines (NILs) differing in nitrogen mobilization during senescence (Jukanti et al 2008). Homologous genes of different classes participating in LEA biosynthesis, antioxidative pathways, and osmolyte synthesis were identified in transcriptomics experiments comparing wheat lines grown under water-stressed conditions (Aprile et al 2009;).…”

Response of wheat ear photosynthesis and photosynthate carbon distribution to water deficit

“…It is also the second largest food crop in China. Drought is the single most important environmental stress that reduces crop yields (Abebe et al 2010). The challenge facing crop breeders is the creation of food crops with increasing resilience to environmental stresses whilst producing higher yields (Steinmeyer et al 2013).…”