Label-free quantitative proteomic analysis of drought stress-responsive late embryogenesis abundant proteins in the seedling leaves of two wheat (Triticum aestivum L.) genotypes.

Late embryogenesis abundant (LEA) proteins are highly hydrophilic proteins with key roles in environmental stress responses. In this study, we performed the first survey of the LEA proteome in seedling leaves from two wheat genotypes subjected to drought stress, i.e., Shaanhe 6 (SH, drought-tolerant) and Zhengyin 1 (ZY, drought-sensitive). After isolating the LEA subpopulation by treating total soluble proteins with heating combined with 1% trichloroacetic acid treatment that was assessed by Western blotting of dehydrins, label-free proteomic analysis identified 38 LEA proteins or homologues belonging to seven LEA subfamilies in the two genotypes. The abundances of over half of the LEA proteins changed significantly after drought stress and they were involved in protection against drought, with at least 20 in SH and 14 in ZY. We found that the common differentially expressed LEA proteins increased in abundance more in the SH genotype compared with the ZY genotype, and six LEA proteins were significantly upregulated exclusively in the SH genotype, which may contribute to higher drought tolerance in SH. We also identified 221 non-LEA proteins from 12 functional categories. Our results provide a deeper understanding of the LEA expression patterns in response to drought stress in two wheat genotypes. SIGNIFICANCE: We identified 38 LEA proteins or homologues from different LEA families in two wheat genotypes, thereby indicating the complex and versatile protective roles of LEA proteins in drought stress resistance. Moreover, the abundance of differentially expressed LEA proteins increased more in the SH genotype compared with the ZY genotype, and several LEA proteins with significant upregulation only in the SH genotype may contribute to its higher tolerance of drought stress. 221 non-LEA proteins were differentially accumulated in at least one of the SH and ZY genotypes. They are involved mainly with 12 biological functions and they might explain different drought responses of the two genotypes. The differentially expressed LEA and non-LEA proteins may be potential markers of drought tolerance to facilitate wheat breeding, particularly those that were specifically upregulated in the SH genotype, or with opposing expression patterns in the two genotypes.