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Background: Members of the Early Salt Induced 3 (Esi3/RCI2/PMP3) gene family in plants have been shown to be induced in response to both biotic and abiotic stresses and to enhance stress tolerance in both transgenic plants and Saccharomyces cerevisiae. Esi3 was first identified as a salt stress induced gene in the salt tolerant wild wheat grass, Lophopyrum elongatum, and subsequently homologous genes in many other species were found to be members of the gene family. These include Arabidopsis thaliana and Oryza sativa where they are referred to as Rare Cold Inducible 2 (RCI2), and Zea mays where they are referred to as Plasma Membrane Protein 3 (PMP3). This study characterizes the Esi3 family members in Triticum aestivum and explores the tissue specific expression patterns of the gene family members as well as their response to a variety of environmental stresses., Results: The Esi3 gene family was found to have a total of 29 family members comprised of ten paralogous groups in the hexaploid T. aestivum. Each paralogous group contains three homeologous copies, one in each of the A, B and D genomes with the exception of Esi3-2 which is missing the B copy. The genes of the Esi3 gene family were also identified in four other monocot species, Aegilops tauschii, Hordeum vulgare, Secale cereale and Sorghum bicolor, and were confirmed or corrected for Brachypodium distachyon, Oryza sativa and Zea mays, as well as the dicot Arabidopsis thaliana. Gene expression of the Esi3s was analyzed using tissue-specific, abiotic and biotic stress RNA-Seq 454 sequence libraries and Affymetrix microarray data for T. aestivum., Conclusions: Members of nearly all paralogous groups of the Esi3 genes in T. aestivum have altered gene expression in response to abiotic or biotic stress conditions. In addition, there are modest differences in gene expression among homeologous members of the gene family. This suggests that the Esi3 gene family plays an important role in the plants response to the stresses presented in this study. The Esi3-9 in T. aestivum has a unique N terminal extension placing it into Group III, a new group for the Esi3/RCI2/PMP3 gene family.

Background: The caleosin genes encode proteins with a single conserved EF hand calcium-binding domain and comprise small gene families found in a wide range of plant species. Some members of the gene family have been shown to be upregulated by environmental stresses including low water availability and high salinity. Caleosin 3 from wheat has been shown to interact with the α-subunit of the heterotrimeric G proteins, and to act as a GTPase activating protein (GAP). This study characterizes the size and diversity of the gene family in wheat and related species and characterizes the differential tissue-specific expression of members of the gene family., Results: A total of 34 gene family members that belong to eleven paralogous groups of caleosins were identified in the hexaploid bread wheat, T. aestivum. Each group was represented by three homeologous copies of the gene located on corresponding homeologous chromosomes, except the caleosin 10, which has four gene copies. Ten gene family members were identified in diploid barley, Hordeum vulgare, and in rye, Secale cereale, seven in Brachypodium distachyon, and six in rice, Oryza sativa. The analysis of gene expression was assayed in triticale and rye by RNA-Seq analysis of 454 sequence sets and members of the gene family were found to have diverse patterns of gene expression in the different tissues that were sampled in rye and in triticale, the hybrid hexaploid species derived from wheat and rye. Expression of the gene family in wheat and barley was also previously determined by microarray analysis, and changes in expression during development and in response to environmental stresses are presented., Conclusions: The caleosin gene family had a greater degree of expansion in the Triticeae than in the other monocot species, Brachypodium and rice. The prior implication of one member of the gene family in the stress response and heterotrimeric G protein signaling, points to the potential importance of the caleosin gene family. The complexity of the family and differential expression in various tissues and under conditions of abiotic stress suggests the possibility that caleosin family members may play diverse roles in signaling and development that warrants further investigation.