Abstract
Heat-shock proteins (HSPs) are ubiquitous proteins with important roles in response to biotic and abiotic stress. The 70-kDa heat-shock genes (Hsp70s) encode a group of conserved chaperone proteins that play central roles in cellular networks of molecular chaperones and folding catalysts across all the studied organisms including bacteria, plants and animals. Several Hsp70s involved in drought tolerance have been well characterized in various plants, whereas no research on Chenopodium quinoa HSPs has been completed. Here, we analyzed the genome of C. quinoa and identified sixteen Hsp70 members in quinoa genome. Phylogenetic analysis revealed the independent origination of those Hsp70 members, with eight paralogous pairs comprising the Hsp70 family in quinoa. While the gene structure and motif analysis showed high conservation of those paralogous pairs, the synteny analysis of those paralogous pairs provided evidence for expansion coming from the polyploidy event. With several subcellular localization signals detected in CqHSP70 protein paralogous pairs, some of the paralogous proteins lost the localization information, indicating the diversity of both subcellular localizations and potential functionalities of those HSP70s. Further gene expression analyses revealed by quantitative polymerase chain reaction (qPCR) analysis illustrated the significant variations of Cqhsp70s in response to drought stress. In conclusion, the sixteen Cqhsp70s undergo lineage-specific expansions and might play important and varied roles in response to drought stress.
Highlights
As sessile organisms, plants are constantly exposed to changing environments that impose stresses on their growth and development
Little is known aboutabout the HSP70 family in quinoa, one of the important and highly nutritious crops with tolerance the HSP70 family in quinoa, one of the important and highly nutritious crops with tolerance to to various stresses
We found that the second duplication event contributed to expansion of HSP70s in Clades B and F, while both genome duplication events were the reason for the expansion of HSP70 in Clade G
Summary
Plants are constantly exposed to changing environments that impose stresses on their growth and development. A more comprehensive phylogenetic tree of Hsp70s derived from 16 plant species was constructed, and the result indicated independent origination of those Hsp genes before speciation of chlorophytes and the 16 Cqhsp70s were classified into eight paralogous pairs. Further analysis of those gene pairs showed high similarities in gene structure, in parallel to the conserved motifs in those paralogous pairs, indicating that the expansion of Cqhsp70s came from the recent polyploidy event. Those expression analyses showed us various patterns of Cqhsp70s between and within Hsp paralogous pairs, indicating the function diversity of those homologs in response to drought stress as well as other possible conditions during plants development
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