TCP transcription factors are important during plant growth and stress responses. However, their role in the cold stress response of Brassica rapa L. remains poorly understood. In this research, we identified the TCPs gene family in B. rapa to learn the features of the BrTCP gene family, functionally annotating the interacting proteins of TCP4 and analyzing their expression levels. Our results illustrated the presence of 19 members of the BrTCPs family in B. rapa, exhibiting molecular weights ranging from 27,367.45 to 59,433.64 Da. All identified proteins were classified as unstable, with isoelectric points ranging from 5.5 to 9.48. Subcellular localization forecasted that TCP proteins were all positioned in the nucleus. The BrTCP gene structure is relatively simple, with only seven members possessing introns, and none of the members contain UTR regions. BrTCPs comprise hormone-, light-, and stress-responsive elements. We found that the frequency of photoresponsive elements was greatest in the promoter region, suggesting that BrTCP genes are regulated by light signals and function synergistically with plant growth and development. In addition, five candidate interaction proteins of BrTCP4 were identified using yeast two-hybrid screening. RNA-Seq and q-PCR analyses of the interacting genes revealed differential expression of BrTCP family genes across various tissues following cold stress. Significant responses were observed under low-temperature stress, drought stress, and rehydration treatment, suggesting that these genes play crucial roles as regulators of the molecular network mechanisms responding to stress. This study enhances our understanding of the BrTCP family and provides significant insights into the stress tolerance mechanisms of B. rapa.

Drought is a major abiotic stress factor that reduces agricultural productivity. Understanding the molecular regulatory network of drought response in winter rape is of great significance for molecular Brassica rapa. In order to comprehensively analyze the network expression of DEGs and DEMIs in winter rape under drought stress, in this study we used Longyou 7 as the experimental material to identify DEGs and DEMIs related to drought stress by transcriptome and miRNA sequencing. A total of 14–15 key differential mRNA genes related to drought stress and biological stress were screened out under different treatments in the three groups. and 32 differential miRNAs were identified through targeted regulatory relationships, and the mRNA expression of 20 target genes was negatively regulated by the targeting regulatory relationship. It is mainly enriched in starch and sucrose metabolism, carbon metabolism and other pathways. Among them, gra-MIR8731-p3_2ss13GA18GA regulated the expression of multiple mRNAs in the three treatments. miRNA is mainly involved in the drought resistance of Chinese cabbage winter rape by regulating the expression of target genes, such as starch and sucrose metabolism, amino acid biosynthesis, and carbon metabolism. These miRNAs and their target genes play an indispensable role in winter rapeseed drought stress tolerance regulation.

The CPA gene family regulates ionic balance and pH homeostasis in cells, significantly contributing to plant stress tolerance. In this study, a total of 63 BrCPA gene family members were identified in the whole genome of Brassica rapa L. (B. rapa), and the three subfamily members were BrNHX (9), BrKEA (15), and BrCHX (39), respectively. The members of the BrCPA gene family encoded 303-1259 amino acids, with molecular weights in the range of 32,860.39~139,884.73 kDa, distributed on 10 chromosomes, and contained 17 conserved motifs, BrNHX and BraKEA, and the BrCPA gene family members had the same molecular weights on 10 chromosomes and contain 17 conserved motifs. The BrNHX and BraKEA subfamilies have more exons than the BrCHX subfamily. An analysis of promoter cis-acting elements in the BrCPA gene showed that members of this gene family contain TC-rich, LTR, MBS, and ARE stress response elements. In addition, transcriptome analysis revealed the expression of CPA genes in B. rapa under salt stress. The selected genes were verified by RT-qPCR. By detecting the Na⁺ and K⁺ flow rates in the root and chloroplast cells of salt-tolerant and salt-sensitive varieties after salt treatment, it was found that the rate of Na⁺ and K⁺ efflux from the root and chloroplast cells of salt-sensitive varieties was significantly higher than that of salt-tolerant varieties. This investigation marks the first systematic identification of the CPA gene family in B. rapa. This study further explores its expression patterns and the efflux rates of Na⁺ and K⁺ across salt-tolerant varieties, providing a theoretical basis for understanding the role of the CPA gene family in the salt stress response of B. rapa.