Abstract
Hsp20 proteins exist in all plant species and represent the most abundant small heat shock proteins (sHSPs) in plants. Hsp20s were known as chaperones maintaining cellular homeostasis during heat or other kinds of abiotic stresses. The objective of this study was to understand the phylogenetic relationship, genomic organization, diversification of motif modules, genome localization, expression profiles, and interaction networks of switchgrass (Panicum virgatum L.) Hsp20s (PvHsp20s). A total of 63 PvHsp20s were identified with their consensus as well as unique ACD motifs and gene structures analyzed. Most PvHsp20s (87%) were responsive to heat and other kinds of abiotic stresses. When under optimum growth condition, 38 of them displayed relative higher expression levels in inflorescence and seeds, suggesting their protective roles in the stress-sensitive reproductive organs. An in silico analysis of interaction network of PvHsp20 proteins further revealed potential interactive proteins, including stress-inducible ones in the network. Furthermore, PvHsp20 genes unevenly distributed in two sets of homeologous chromosomes, and only segmental duplication was found among the paralogous gene pairs, reflecting that the allotetraploidization of switchgrass allowed the accumulation of PvHsp20s that in turn facilitated its successful adaptation in hot and dry plateaus of North America. The present results provided an insight into PvHsp20s with an emphasis on the uniqueness of this gene family in switchgrass. Such information shall also be useful in functional studies of PvHsp20 genes and molecular breeding of switchgrass.
Highlights
Plants are often exposed to a variety of abiotic stresses such as heat, cold, drought, and salt, etc
Hsp20s, or small heat shock proteins, have molecular sizes ranging from 15 to 42 kDa, functioning as molecular chaperones to keep the stability of proteins in an ATP-independent manner, that is crucial for cellular thermotolerance (Guo et al, 2015)
A total of 92 proteins containing alpha crystallin domain (ACD) were identified in switchgrass from the newly released switchgrass genome database (Panicum virgatum JGI v1.1), and detailed information about these proteins were presented in Supplementary File 1
Summary
Plants are often exposed to a variety of abiotic stresses such as heat, cold, drought, and salt, etc. Hsp20s, or small heat shock proteins (sHSPs), have molecular sizes ranging from 15 to 42 kDa, functioning as molecular chaperones to keep the stability of proteins in an ATP-independent manner, that is crucial for cellular thermotolerance (Guo et al, 2015). Another cardinal characteristic of Hsp proteins is the presence of a highly conserved 80 to 100 amino acid sequence, referred to as the alpha crystallin domain (ACD), seated in the proteins C-terminal region, and this ACD has two consensus sequences at its Cand N-terminals with 29 aa and 27 aa in length, respectively
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