Characteristics and expression of the TCP transcription factors family in Allium senescens reveal its potential roles in drought stress responses

Allium senescens, is an important economic and ecological grassland plant with drought-resistant characteristics. A TCP protein transcription factor is important in the regulation of plant development and adverse responses. However, the mechanism by which TCP transcription functions in drought resistance in Allium senescens is still not clear. Here, we obtained a total of 190,305 transcripts with 115,562 single gene clusters based on RNA-Seq sequencing of Allium senescens under drought stress. The total number of bases was 97,195,096 bp, and the average length was 841.06 bp. Furthermore, we found that there were eight genes of the TCP family that showed an up regulated expression trend under drought stress in Allium senescens. We carried out an investigation to determine the evolution and function of the AsTCP family and how they produce an effect in drought resistance. The 14 AsTCP genes were confirmed and divided into class I and class II containing CIN and CYC/TBI subfamilies, respectively. We also found that the expression of AsTCP17 was remarkably upregulated with drought treatment. Besides, the transformation of AsTCP17 in Arabidopsis revealed that the protective enzymes, namely polyphenol oxidase (POD) and superoxide dismutase (SOD), were increased by 0.4 and 0.8 times, respectively. Chlorophyll content was also increased, while the H2O2 and malondialdehyde (MDA) contents were decreased. Staining assays with 3,3 '- diaminobenzidine (DAB) also suggested that the AsTCP17 downregulates reactive oxygen species (ROS) accumulation. In addition, overexpression of the AsTCP17 affected the accumulation of drought-related hormones in plants, and the synthesis of ABA. The expression of AtSVP and AtNCED3, related ABA synthesis pathway genes, indicated that the level of expression of AtSVP and AtNCED3 was obviously enhanced, with the overexpression of line 6 showing a 20.6-fold and 7.0-fold increase, respectively. Taken together, our findings systematically analyze the AsTCPs family at the transcriptome expression level in Allium senescens, and we also demonstrated that AsTCP17 protein, as a positive regulator, was involved in drought resistance of Allium senescens. In addition, our research contributes to the comprehensive understanding of the drought stress defense mechanism in herbaceous plants.