Abstract
BackgroundThe Hsp20 genes are associated with stress caused by HS and other abiotic factors, but have recently been found to be associated with the response to biotic stresses. These genes represent the most abundant class among the HSPs in plants, but little is known about this gene family in soybean. Because of their apparent multifunctionality, these proteins are promising targets for developing crop varieties that are better adapted to biotic and abiotic stresses. Thus, in the present study an in silico identification of GmHsp20 gene family members was performed, and the genes were characterized and subjected to in vivo expression analysis under biotic and abiotic stresses.ResultsA search of the available soybean genome databases revealed 51 gene models as potential GmHsp20 candidates. The 51 GmHsp20 genes were distributed across a total of 15 subfamilies where a specific predicted secondary structure was identified. Based on in vivo analysis, only 47 soybean Hsp20 genes were responsive to heat shock stress. Among the GmHsp20 genes that were potentials HSR, five were also cold-induced, and another five, in addition to one GmAcd gene, were responsive to Meloidogyne javanica infection. Furthermore, one predicted GmHsp20 was shown to be responsive only to nematode infection; no expression change was detected under other stress conditions. Some of the biotic stress-responsive GmHsp20 genes exhibited a divergent expression pattern between resistant and susceptible soybean genotypes under M. javanica infection. The putative regulatory elements presenting some conservation level in the GmHsp20 promoters included HSE, W-box, CAAT box, and TA-rich elements. Some of these putative elements showed a unique occurrence pattern among genes responsive to nematode infection.ConclusionsThe evolution of Hsp20 family in soybean genome has most likely involved a total of 23 gene duplications. The obtained expression profiles revealed that the majority of the 51 GmHsp20 candidates are induced under HT, but other members of this family could also be involved in normal cellular functions, unrelated to HT. Some of the GmHsp20 genes might be specialized to respond to nematode stress, and the predicted promoter structure of these genes seems to have a particular conserved pattern related to their biological function.
Highlights
IntroductionThe Hsp genes are associated with stress caused by Heat shock (HS) and other abiotic factors, but have recently been found to be associated with the response to biotic stresses
The Heat shock protein 20 (Hsp20) genes are associated with stress caused by HS and other abiotic factors, but have recently been found to be associated with the response to biotic stresses
The soybean Hsp20 genes are distributed across 17 chromosomes, where gene duplication events have most likely resulted in expansion of the family, most notably for the CI subfamily
Summary
The Hsp genes are associated with stress caused by HS and other abiotic factors, but have recently been found to be associated with the response to biotic stresses These genes represent the most abundant class among the HSPs in plants, but little is known about this gene family in soybean. Because of their apparent multifunctionality, these proteins are promising targets for developing crop varieties that are better adapted to biotic and abiotic stresses. Plants inevitably interact with climatic factors and are often subjected to different types of biotic and abiotic stresses Environmental stress conditions, such as those related to drought, flooding, salinity, cold, heat, chemical substances derived from human activities and pathogens, have adverse effects on plant growth and crop yields [1,2]. The signals or specific factors that trigger the expression of Hsps genes during biotic stress are currently unknown, but the metabolic changes resulting from pathogen attack can generate similar signals or stimuli as those observed under abiotic stress activation [14,15]
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