Guoli Zhang

Cabbage is a heat-stress-sensitive cool-season crop. When exposed to high temperatures, cabbage plants can experience reduced growth, wilting, leaf yellowing, and premature bolting (the formation of a flowering stem). The regulatory mechanism controlling heat stress is poorly understood in cabbage. To investigate this mechanism, physiological changes and transcriptional profiling for different heat treatment times were analyzed in this study. The results showed that superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were enhanced under heat stress. In particular, the increase in SOD and POD activities after 12 h of heat treatment was greater than that after 4 h of heat treatment. With increasing heat treatment duration, the leaf CAT activity and H₂O₂ content decreased after the initial increase. The electrolyte leakage and malondialdehyde (MDA) content dropped significantly, while the proline content increased. Alongside that, 7007 and 5537 upregulated genes were identified in the experimental group treated with heat stress for the 4 h and 12 h treatments, respectively. We found that 10,479 DEGs were shared in the heat stress treatment, of which 1241 were associated with the heat treatment time. By integrating the expression patterns and functional annotations of genes related to heat stress, we identified 15 hub genes that respond to heat stress in cabbage. Meanwhile, we had constructed a physiological to molecular model of cabbage response to long-term heat stress. These findings provide new insights for the comprehensive analysis of cabbage response to heat stress and genetic resources for breeding new varieties of cabbage with heat tolerance via genetic engineering.

The completion of more and more high-quality cabbage genome sequencing attempts provides an important reference genome sequence for resequencing a large proportion of B. oleracea populations. This has laid a foundation for the study of the population diversity of B. oleracea and the excavation of genes related to important agronomic traits. Here, we performed genome resequencing of 91 B. oleracea accessions from 14 countries. We produced a total of 983.84 Gb of high-quality sequencing data, and the average sequencing depth of the genomes was over 15.71 among the 91 accessions. A total of 3,432,341 high-quality SNPs were detected in these B. oleracea accessions. A phylogenetic tree indicated that the leaf ball shapes of “Gaobian” accessions and most “Jianqiu” accessions converge with “Bianqiu” accessions, while “Yuanqiu” accessions were individually assigned to a branch. The principal component analysis (PCA) result was consistent with the phylogenetic relationships. The LD distance of “Yuanqiu” was 38.69 Kb, while that of “Bianqiu” was 30.16 Kb. This result indicated that the linkage degree of the “Yuanqiu” population is greater than that of the “Bianqiu” population, which may indicate that the “Yuanqiu” population has received more positive selection. Our analysis showed that, for the 91 accessions, the best population structure number was four. A total of 560 genes were identified across the 203 selected sweep regions identified in the “Yuanqiu” accessions. Similarly, 682 genes were identified across the 304 selective sweep regions in the “Bianqiu” accessions. Finally, several functional terms were identified via enrichment analysis of the genes in the selective sweep regions. In conclusion, this study will provide rich resources for studies on gene function related to leaf ball development and the population diversity of B. olearcea.