Identification and analysis of differentially expressed trihelix genes in maize () under abiotic stresses.

BACKGROUND

Trihelix transcription factors play important roles in triggering plant growth and imparting tolerance against biotic and abiotic stresses. However, a systematical analysis of the trihelix transcription factor family under heat and drought stresses in maize has not been reported.

METHODS

PlantTFDB and TBtools were employed to identify the trihelix domain-containing genes in the maize genome. The heat-regulated transcriptome data for maize were obtained from NCBI to screen differentially expressed genes through statistical analysis. The basic protein sequences, chromosomal localization, and subcellular localization were analyzed using Maize GDB, Expasy, SOMPA, TBtools, and Plant-mPLoc. The conserved motifs, evolutionary relationships, and -elements, were analyzed by MEME, MEGA7.0 and PlantCARE software, respectively. The tissue expression patterns of and their expression profiles under heat and drought stress were detected using quantitative real-time PCR (qRT-PCR).

RESULTS

A total of 44 trihelix family members were discovered, and members were distributed over 10 chromosomes in the maize genome. A total of 11 genes were identified that were regulated by heat stress; these were unevenly distributed on chromosomes 1, 2, 4, 5, and 10. encoded a total of 16 proteins, all of which were located in the nucleus; however, ZmTH04.1 was also distributed in the chloroplast. The protein length varied from 206 to 725 amino acids; the molecular weight ranged from 22.63 to 76.40 kD; and the theoretical isoelectric point (pI) ranged from 5.24 to 11.2. The protein's secondary structures were mainly found to be random coils and α-helices, with fewer instances of elongation chains and β-rotations. Phylogenetic relationship analysis showed that these can be divided into five sub-groups. The conserved domain of was GT1 or MyB_DNA-Bind_4. The protein and gene structure of differed greatly among the subfamilies, while the structures within the subfamilies were similar. The promoter of contained abundant tissue-specific expression -acting elements and abiotic stress response elements. qRT-PCR analysis showed that expression levels were significantly different in different tissues. Furthermore, the expression of was dramatically up-regulated by heat stress, while the expression of , , , , , , , and were down-regulated by heat stress. Upon PEG-simulated drought stress, was significantly up-regulated, while and were down-regulated.

CONCLUSIONS

We performed a genome-wide, systematic identification and analysis of differentially expressed trihelix genes under heat and drought stresses in maize.