Heat shock proteins (Hsps) are essential components in plant tolerance mechanism under various abiotic stresses. Hsp20 is the major family of heat shock proteins, but little of Hsp20 family is known in potato (Solanum tuberosum), which is an important vegetable crop that is thermosensitive. To reveal the mechanisms of potato Hsp20s coping with abiotic stresses, analyses of the potato Hsp20 gene family were conducted using bioinformatics-based methods. In total, 48 putative potato Hsp20 genes (StHsp20s) were identified and named according to their chromosomal locations. A sequence analysis revealed that most StHsp20 genes (89.6%) possessed no, or only one, intron. A phylogenetic analysis indicated that all of the StHsp20 genes, except 10, were grouped into 12 subfamilies. The 48 StHsp20 genes were randomly distributed on 12 chromosomes. Nineteen tandem duplicated StHsp20s and one pair of segmental duplicated genes (StHsp20-15 and StHsp20-48) were identified. A cis-element analysis inferred that StHsp20s, except for StHsp20-41, possessed at least one stress response cis-element. A heatmap of the StHsp20 gene family showed that the genes, except for StHsp20-2 and StHsp20-45, were expressed in various tissues and organs. Real-time quantitative PCR was used to detect the expression level of StHsp20 genes and demonstrated that the genes responded to multiple abiotic stresses, such as heat, salt or drought stress. The relative expression levels of 14 StHsp20 genes (StHsp20-4, 6, 7, 9, 20, 21, 33, 34, 35, 37, 41, 43, 44 and 46) were significantly up-regulated (more than 100-fold) under heat stress. These results provide valuable information for clarifying the evolutionary relationship of the StHsp20 family and in aiding functional characterization of StHsp20 genes in further research.

Plant basic/helix–loop–helix (bHLH) transcription factors participate in a number of biological processes, such as growth, development and abiotic stress responses. The bHLH family has been identified in many plants, and several bHLH transcription factors have been functionally characterized in Arabidopsis. However, no systematic identification of bHLH family members has been reported in potato (Solanum tuberosum). Here, 124 StbHLH genes were identified and named according to their chromosomal locations. The intron numbers varied from zero to seven. Most StbHLH proteins had the highly conserved intron phase 0, which accounted for 86.2% of the introns. According to the Neighbor-joining phylogenetic tree, 259 bHLH proteins acquired from Arabidopsis and potato were divided into 15 groups. All of the StbHLH genes were randomly distributed on 12 chromosomes, and 20 tandem duplicated genes and four pairs of duplicated gene segments were detected in the StbHLH family. The gene ontology (GO) analysis revealed that StbHLH mainly function in protein and DNA binding. Through the RNA-seq and quantitative real time PCR (qRT-PCR) analyses, StbHLH were found to be expressed in various tissues and to respond to abiotic stresses, including salt, drought and heat. StbHLH1, 41 and 60 were highly expressed in flower tissues, and were predicted to be involved in flower development by GO annotation. StbHLH45 was highly expressed in salt, drought and heat stress, which suggested its important role in abiotic stress response. The results provide comprehensive information for further analyses of the molecular functions of the StbHLH gene family.

WRKY transcription factors play pivotal roles in regulation of stress responses. This study identified 79 WRKY genes in potato (Solanum tuberosum). Based on multiple sequence alignment and phylogenetic relationships, WRKY genes were classified into three major groups. The majority of WRKY genes belonged to Group II (52 StWRKYs), Group III had 14 and Group I consisted of 13. The phylogenetic tree further classified Group II into five sub-groups. All StWRKY genes except StWRKY79 were mapped on potato chromosomes, with eight tandem duplication gene pairs and seven segmental duplication gene pairs found from StWRKY family genes. The expression analysis of 22 StWRKYs showed their differential expression levels under various stress conditions. Cis-element prediction showed that a large number of elements related to drought, heat and salicylic acid were present in the promotor regions of StWRKY genes. The expression analysis indicated that seven StWRKYs seemed to respond to stress (heat, drought and salinity) and salicylic acid treatment. These genes are candidates for abiotic stress signaling for further research.

Arabinogalactan proteins (AGPs) are a family of extracellular glycoproteins implicated in plant growth and development. With a rapid growth in the number of genomes sequenced in many plant species, the family members of AGPs can now be predicted to facilitate functional investigation. Building upon previous advances in identifying Arabidopsis AGPs, an integrated strategy of systematical AGP screening for “classical” and “chimeric” family members is proposed in this study. A Python script named Finding-AGP is compiled to find AGP-like sequences and filter AGP candidates under the given thresholds. The primary screening of classical AGPs, Lys-rich classical AGPs, AGP-extensin hybrids, and non-classical AGPs was performed using the existence of signal peptides as a necessary requirement, and BLAST searches were conducted mainly for fasciclin-like, phytocyanin-like and xylogen-like AGPs. Then glycomodule index and partial PAST (Pro, Ala, Ser, and Thr) percentage are adopted to identify AGP candidates. The integrated strategy successfully discovered AGP gene families in 47 plant species and the main results are summarized as follows: (i) AGPs are abundant in angiosperms and many “ancient” AGPs with Ser-Pro repeats are found in Chlamydomonas reinhardtii; (ii) Classical AGPs, AG-peptides, and Lys-rich classical AGPs first emerged in Physcomitrella patens, Selaginella moellendorffii, and Picea abies, respectively; (iii) Nine subfamilies of chimeric AGPs are introduced as newly identified chimeric subfamilies similar to fasciclin-like, phytocyanin-like and xylogen-like AGPs; (iv) The length and amino acid composition of Lys-rich domains are largely variable, indicating an insertion/deletion model during evolution. Our findings provide not only a powerful means to identify AGP gene families but also probable explanations of AGPs in maintaining the plant cell wall and transducing extracellular signals into the cytoplasm.

Background: N6-methyladenosine (m6A) is the most prevalent post-transcriptional modification of eukaryotic mRNA. It has been reported that there is a stimulus-dependent regulation of m6A in the mammalian central nervous system in response to sensory experience, learning, and injury. The mRNA m6A methylation pattern in rat cortex after traumatic brain injury (TBI) has not been investigated. Results: In this study, we conducted a genome-wide profiling of mRNA m6A methylation in rat cortex via methylated RNA immunoprecipitation sequencing (MeRIP-Seq). After TBI, the expressions of METTL14 and FTO were significantly down-regulated in rat cerebral cortex. Using MeRIP-Seq, we identified a total of 2165 significantly changed peaks, of which 1062 were significantly up-regulated and 1103 peaks were significantly down-regulated. These m6A peaks were located across 1850 genes. The analysis of both m6A peaks and mRNA expression revealed that there were 175 mRNA significantly altered methylation and expression levels after TBI. Moreover, it was found that functional FTO is necessary to repair neurological damage caused by TBI but has no effect on the spatial learning and memory abilities of TBI rats by using FTO inhibitor FB23–2. Conclusion: This study explored the m6A methylation pattern of mRNA after TBI in rat cortex and identified FTO as possible intervention targets in the epigenetic modification of TBI.

The plant hormone auxin plays pivotal roles in many aspects of plant growth and development. The auxin/indole-3-acetic acid (Aux/IAA) gene family encodes short-lived nuclear proteins acting on auxin perception and signaling, but the evolutionary history of this gene family remains to be elucidated. In this study, the Aux/IAA gene family in 17 plant species covering all major lineages of plants is identified and analyzed by using multiple bioinformatics methods. A total of 434 Aux/IAA genes was found among these plant species, and the gene copy number ranges from three (Physcomitrella patens) to 63 (Glycine max). The phylogenetic analysis shows that the canonical Aux/IAA proteins can be generally divided into five major clades, and the origin of Aux/IAA proteins could be traced back to the common ancestor of land plants and green algae. Many truncated Aux/IAA proteins were found, and some of these truncated Aux/IAA proteins may be generated from the C-terminal truncation of auxin response factor (ARF) proteins. Our results indicate that tandem and segmental duplications play dominant roles for the expansion of the Aux/IAA gene family mainly under purifying selection. The putative nuclear localization signals (NLSs) in Aux/IAA proteins are conservative, and two kinds of new primordial bipartite NLSs in P. patens and Selaginella moellendorffii were discovered. Our findings not only give insights into the origin and expansion of the Aux/IAA gene family, but also provide a basis for understanding their functions during the course of evolution.