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.

Brassica rapa L. is an important overwintering oilseed crop in Northwest China. Histone acetyltransferases (HATs) play an important role in epigenetic regulation, as well as the regulation of plant growth, development, and responses to abiotic stresses. To clarify the role of histone acetylation in the low-temperature response of B. rapa L., we identified 29 HAT genes in B. rapa L. using bioinformatics tools. We also conducted a comprehensive analysis of the physicochemical properties, gene structure, chromosomal localization, conserved structural domains and motifs, cis-acting regulatory elements, and evolutionary relationships of these genes. Using transcriptome data, we analyzed the expression patterns of BrHAT family members and predicted interactions between proteins; the results indicated that BrHATs play an important role in the low-temperature response of B. rapa L. HAT inhibitor (curcumin; CUR) and histone deacetylase inhibitor (Trichostatin A; TSA) were applied to four B. rapa L. varieties varying in cold resistance under the same low-temperature conditions, and changes in the physiological indexes of these four varieties were analyzed. The inhibitor treatment attenuated the effect of low temperature on seed germination, and curcumin treatment was most effective, indicating that the germination period was primarily regulated by histone acetylase. Both inhibitor treatments increased the activity of protective enzymes and the content of osmoregulatory substances in plants, suggesting that histone acetylation and deacetylation play a significant role in the response of B. rapa L. to low-temperature stress. The qRT-PCR analyses showed that the expression patterns of BrHATs were altered under different inhibitor treatments and low-temperature stress; meanwhile, we found three significantly differentially expressed genes. In sum, the process of histone acetylation is involved in the cold response and the BrHATs gene plays a role in the cold stress response.

N6-methyladenosine (m⁶A) is an mRNA modification considered essential in plants, and is a key player in gene regulation at the transcriptional and translational levels. In present study, we mapped Brassica rapa's whole transcriptome m⁶A profile under low-temperature stress in different cold tolerant varieties to elucidate the m⁶A methylation pattern. The distribution of m⁶A modifications changed significantly under low temperature stress. More 5'UTR m⁶A was deposited in strong cold-resistant varieties and responded positively to cold resistance by regulating mRNA expression abundance. The increase in m⁶A abundance was correlated with the increase in mRNA abundance after low temperature stress. ZAT12 might positively regulate its mRNA expression through m⁶A methylation. MYBC1 might be a negative regulator to cope with low-temperature stress. The hypothetical protein was involved in starch and sucrose metabolic pathways, and that the Low-quality protein was involved in the regulation of DNA binding, DNA-binding, transcription factor activity, and proline biosynthetic processes and leaf senescence pathways. In addition, a number of m⁶A methyltransferases and m⁶A demethylases play crucial roles in response to cold stress. These results revealed the critical role of m⁶A -modified genes under cold stress and provide new insights into the study of cold resistance in winter Brassica rapa.

During a prolonged domestication and environmental selection, Brassica rapa has formed diverse morphological types during a cultivation process of up to 8000 years, such as root-type turnips (Brassica rapa var. rapa), leaf-type Chinese cabbage (Brassica rapa var. pekinensis), oil-type rapeseed (Brassica rapa L.), and other rich types. China is one of the origins of Brassica rapa L., which is spread all over the east, west, south, and north of China. Studying its origin and evolution holds significant importance for unraveling the cultivation history of Chinese oilseed crops, intraspecific evolutionary relationships, and the utilization value of genetic resources. This article summarizes the cultivation history, evolution, classification research progress, and germplasm resource diversity of Brassica rapa var. oleifera in China. Combining karyotype analysis, genomic information, and wild relatives of Brassica rapa var. oleifera discovered on the Qinghai–Tibet Plateau, it is proposed that Brassica rapa var. oleifera has the characteristic of polycentric origin, and Gansu Province in China is one of the earliest regions for its cultivation. Brassica rapa var. oleifera, originating from the Mediterranean region, was diffused to the East Asian continent through two independent transmission paths (one via the Turkish Plateau and the other via Central Asia and Siberia). Analyzing the genetic diversity characteristics and evolutionary trajectories of these two transmission paths lays a foundation for clarifying the origin and evolutionary process of Brassica rapa var. oleifera and accelerating the breeding of Brassica rapa var. oleifera in China. Despite existing research on the origin of Brassica rapa L., the domestication process of this species remains unresolved. Future studies will employ whole-genome resequencing to address this fundamental question.

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.