Abstract
Late embryogenesis abundant (LEA) proteins, the space fillers or molecular shields, are the hydrophilic protective proteins which play an important role during plant development and abiotic stress. The systematic survey and characterization revealed a total of 68 LEA genes, belonging to 8 families in Sorghum bicolor. The LEA-2, a typical hydrophobic family is the most abundant family. All of them are evenly distributed on all 10 chromosomes and chromosomes 1, 2, and 3 appear to be the hot spots. Majority of the S. bicolor LEA (SbLEA) genes are intron less or have fewer introns. A total of 22 paralogous events were observed and majority of them appear to be segmental duplications. Segmental duplication played an important role in SbLEA-2 family expansion. A total of 12 orthologs were observed with Arabidopsis and 13 with Oryza sativa. Majority of them are basic in nature, and targeted by chloroplast subcellular localization. Fifteen miRNAs targeted to 25 SbLEAs appear to participate in development, as well as in abiotic stress tolerance. Promoter analysis revealed the presence of abiotic stress-responsive DRE, MYB, MYC, and GT1, biotic stress-responsive W-Box, hormone-responsive ABA, ERE, and TGA, and development-responsive SKn cis-elements. This reveals that LEA proteins play a vital role during stress tolerance and developmental processes. Using microarray data, 65 SbLEA genes were analyzed in different tissues (roots, pith, rind, internode, shoot, and leaf) which show clear tissue specific expression. qRT-PCR analysis of 23 SbLEA genes revealed their abundant expression in various tissues like roots, stems and leaves. Higher expression was noticed in stems compared to roots and leaves. Majority of the SbLEA family members were up-regulated at least in one tissue under different stress conditions. The SbLEA3-2 is the regulator, which showed abundant expression under diverse stress conditions. Present study provides new insights into the formation of LEAs in S. bicolor and to understand their role in developmental processes under stress conditions, which may be a valuable source for future research.
Highlights
Environmental stresses such as drought, salinity, high and low temperatures, metals, radiation, and diseases cause extensive damage to crop plants by bringing about the changes in gene regulation and metabolism leading to reduced productivity [1]
The genes are grouped into 8 sub-families like late embryogenesis abundant (LEA) 1–6, dehydrins, and seed maturation proteins (SMP) based on their conserved domains and Pfam nomenclature
A systematic genome-wide analysis resulted in the identification of a total of 68 LEA genes in Sorghum, which are classified into 8 groups and distributed on all the chromosomes
Summary
Environmental stresses such as drought, salinity, high and low temperatures, metals, radiation, and diseases cause extensive damage to crop plants by bringing about the changes in gene regulation and metabolism leading to reduced productivity [1]. To combat the stress conditions, plants develop defense-responsive pathways with the help of regulatory and functional genes [2]. The functional group of genes, mostly the Ca2+-dependent signaling molecules activate the late embryogenesis abundant (LEA)-type genes, which are protective proteins that help in damage repair of plants under diverse abiotic stress conditions [3]. LEAs have been reported to be responsive to various developmental processes and to abiotic stresses like drought, low temperature, salt, and ABA [8,9]. LEAs act as membrane protectors and stabilizers, ion chelators, hydration buffers and antioxidants [9]
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