**1. Introduction**

Abiotic stresses from increasing temperature or salinity can disrupt optimal plant performance and cause significant crop yield losses [1]. To maintain proper homeostasis for normal growth, plants have evolved multiple ways to combat harsh environments by mobilizing a wide spectrum of stress responsive genes [2]. For example, proteins encoded by the *late embryogenesis abundant* (LEA) family genes are known to play defensive roles in plants during abiotic stresses [3,4]. The *LEA* family genes were first studied in cotton seed at the late phases of seed development [4]. The *LEA* family genes were later identified in various tissues of many other plant species and the proteins encoded by these genes were shown to be important during cold, drought and/or high salinity stresses [5,6]. LEA proteins are not plant specific, they are also found in invertebrates, fungi and bacteria [7,8]. Typical LEA proteins are highly hydrophilic due to high contents of charged amino acid residues, as well as amino acids like threonine, serine and alanine residues in their sequences [9]. It was suggested that LEA proteins have molecular shield functions [10] and are capable of abating protein aggregation and preventing enzyme degradation [11], thereby promoting proper cellular homeostasis during stresses [8,12]. LEA proteins are also flexible proteins which can undergo conformational changes and interact with other macromolecules including proteins, membranes and/or nucleic acids during different adverse stress conditions [10].

LEA proteins are divided into at least eight distinct subfamilies, based on their conserved protein domains in the Pfam database: LEA (1–6), Dehydrin and Seed Maturation Protein (SMP) [13]. Motif structures within subfamily genes are mostly conserved, except the genes in the *LEA\_2/LEA5C* subfamily [9]. In addition, proteins in the LEA\_2/LEA5C subfamily are known to have other non-canonical LEA protein properties like high hydrophobicity and at least one atypical LEA domain known as Water stress and Hypersensitive response (WHy) domain. The presence of atypical LEA domain(s) in LEA proteins indicate that these proteins may function differently from typical LEA proteins [14–16]. Proteins in the Dehydrin subfamily are featured with at least one K-segment, a 15 amino acid residue rich in lysine (i.e., EKKGIMDKIKEKLPG) and can function like chaperones to protect peripheral membrane and proteins during dehydration [2,17–20]. Numerous earlier studies have demonstrated that the *LEA* family genes are potential abiotic stress responsive genes, important for enhancing plant stress tolerance. For instance, transgenic Arabidopsis [21,22], maize [23], alfalfa [24] bacteria [25], yeast and tobacco [26] expressing different *LEA* genes exhibited improved abiotic stress tolerance compared with their respective wild-type plant, bacteria or yeast.

*C. songorica* is a xerophyte C4 desert plant distributed widely in the wild lands in the northwest part of China, with an annual precipitation of about 100 mm [27]. Previous genome-wide surveys of *LEA* family genes were done for multiple plant species except perennial monocotyledonous species. In this study, we investigated the *LEA* family genes in *C. songorica* and analyzed the responses of four selected *LEA* genes to heat stress or abscisic acid (ABA) treatment in leaves and shoots. Results from this study provide new information on the evolution of the LEA family proteins, protein structures and potential applications of these genes for the improvement of crop tolerance against abiotic stresses.
