HVA1, a member of LEA3 (late embryogenesis abundant protein, group 3), is closely related to water stress. However, the response of HVA1 to drought remains unknown in hulless barley. In this study, cultivars with high (Handizi), intermediate (Kunlun 12), and low (Dama) drought tolerance were selected from 28 hulless barley cultivars from the Tibet-Qinghai plateau to explore the drought response mechanism of HVA1. Then, HVA1 was cloned and the expression of the three cultivars was studied using exposure to polyethylene glycol (PEG) 6000. HVA1s in the three hulless barleys were highly homologous at the nucleotide and amino acid levels with over 99% identity. Real-time quantitative polymerase chain reaction showed that the expression level of HVA1 induced by PEG 6000 had a single peak curve in the three cultivars, but higher HVA1 transcript accumulation was seen in Handizi than in Kunlun 12 and Dama under the same drought stress. This result was also proved in eight hulless barleys. The expression level was a better predictor of drought resistance than the genetic structure of HVA1.
IntroductionHulless barley (Hordeum vulgare L. var. nudum Hook. f.) is a selfing annual species, with naked grains when ripening. It is widely grown on the Qinghai-Tibet plateau (suffering serious drought stress) and has been a staple food for the Tibetan people since the fifth century CE (Liang et al., 2012). Drought is an important environmental constraint that limits the productivity of barley and other crops worldwide (Romanek et al., 2011). The growth and development of plants are restrained under the stress of drought with decreases in net photosynthetic rate, respiration, leaf osmoregulation ability, and cell membrane stability (Li et al., 2016). The most susceptible stages to drought are germination, early seedling growth, and grain filling. If plants can survive drought stress during these sensitive periods, the ability of the plant to survive additional drought exposure will increase (Liang et al., 2016).Plants have developed many physiological and biochemical reactions in response to adverse environmental conditions. Some compatible low-molecular-weight metabolites will be accumulated to protect cells against dehydration, and the most common of these is late embryogenesis abundant protein (LEA) (Park et al., 2003). LEA proteins are closely related to desiccation induced and regulated by abscisic acid (ABA) or dehydration signaling (Ramanjulu and Bartels, 2002). LEA proteins are involved in protection mechanisms against environmental stressors in plants (Liang et al., 2013). According to the homology of the amino acid sequence and presence of special primitive sequences, LEA proteins are categorised into six groups (Wise, 2003). The Hordeum vulgare aleurone1 (HVA1) gene, which belongs to group 3 LEA, is activated during cell dehydration caused by water deficit, salt stress, low temperature, or ABA induction (Romanek et al., 2011;Battaglia et al., 2008).Most researches on the HVA1 have focused on transformation. The H...