With the burgeoning population of the world, the successful germination of seeds to achieve maximum crop production is very important. Seed germination is a precise balance of phytohormones, light, and temperature that induces endosperm decay. Abscisic acid and gibberellins—mainly with auxins, ethylene, and jasmonic and salicylic acid through interdependent molecular pathways—lead to the rupture of the seed testa, after which the radicle protrudes out and the endosperm provides nutrients according to its growing energy demand. The incident light wavelength and low and supra-optimal temperature modulates phytohormone signaling pathways that induce the synthesis of ROS, which results in the maintenance of seed dormancy and germination. In this review, we have summarized in detail the biochemical and molecular processes occurring in the seed that lead to the germination of the seed. Moreover, an accurate explanation in chronological order of how phytohormones inside the seed act in accordance with the temperature and light signals from outside to degenerate the seed testa for the thriving seed’s germination has also been discussed.

Pectobacterium carotovorum ssp. carotovorum (Pcc) is a necrotrophic bacterial species that causes soft rot disease in Chinese cabbage. In this study, plants harboring the resistant mutant sr gene, which confers resistance against Pcc, were screened from an 800 M₂ population mutated by ethyl methane sulfonate (EMS) and scored in vitro and in vivo for lesion size. The transcript profiles showed ~512 differentially expressed genes (DEGs) between sr and WT plants occurring between 6 and 12 h postinoculation (hpi), which corresponded to the important defense regulation period (resistance) to Pcc in Chinese cabbage. The downstream defense genes (CPK, CML, RBOH MPK3, and MPK4) of pathogen pattern-triggered immunity (PTI) were strongly activated during infection at 12 hpi in resistant mutant sr; PTI appears to be central to plant defense against Pcc via recognition by three putative pattern recognition receptors (PRRs; BrLYM1-BrCERK1, BrBKK1/SERK4-PEPR1, BrWAKs). Pcc triggered the upregulation of the jasmonic acid (JA) and ethylene (ET) biosynthesis genes in mutant sr, but auxins and other hormones may have affected some negative signals. Endogenous hormones (auxins, JAs, and SA), as well as exogenous auxins (MEJA and BTH), were also verified as functioning in the immune system. Concurrently, the expression of glucosinolate and lignin biosynthesis genes was increased at 12 hpi in resistant mutant sr, and the accumulation of glucosinolate and lignin also indicated that these genes have a functional defensive role against Pcc. Our study provides valuable information and elucidates the resistance mechanism of Chinese cabbage against Pcc infection.

The genus Brassica contains a rich diversity of species and morphological types, including leaf, root, and oil crops, all of which show substantial phenotypic variation. Both Chinese cabbage and cabbage are typical leaf-type crops with normal roots. We created translocation lines based on interspecific crosses between Chinese cabbage and cabbage and identified qdh225, which exhibited a swollen-root phenotype. The swollen root of qdh225 contained a large number of granular substances, and the formation of its irregular morphological tissue was caused by a thickening of the phloem. Transcriptomic and metabolomic data suggested that differential expression of genes encoding nine types of enzymes involved in starch and sucrose metabolism caused changes in starch synthesis and degradation in the swollen root. These genes jointly regulated sucrose and starch levels, leading to significant enrichment of starch and soluble proteins in the swollen root and a reduction in the content of soluble sugars such as D-glucose and trehalose 6-phosphate. A significant increase in IAA and ABA contents and a decrease in GA content in the swollen root likely promoted the differential expression of genes associated with hormone signal transduction, thereby regulating the development of the swollen root. Taken together, our data suggest that accumulation of IAA and ABA and reduction in GA promote swollen root formation by regulating hormone-mediated signaling, leading to a thickening of phloem, root enlargement, and substantial accumulation of starch and soluble proteins. The latter provide materials, energy, and nutrient sources for the development of swollen roots.

Five monosomic alien addition lines (MAALs) of Brassica rapa ssp. pekinensis – B. oleracea var. capitata were obtained by hybridization and backcrossing between B. rapa ssp. pekinensis (female parent) and B. oleracea var. capitata. The alien linkage groups were identified using 42 B. oleracea var. capitata linkage group-specific markers as B. oleracea linkage groups C2, C3, C6, C7 and C8. Based on the chromosomal karyotype of root tip cells, these five MAALs added individual chromosomes from B. oleracea var. capitata: chr 1 (the longest), chr 2 or 3, chr 5 (small locus of 25S rDNA), chr 7 (satellite-carrying) and chr 9 (the shortest). Five disomic alien addition lines were then generated by selfing their corresponding MAALs.

Whole‐genome duplication is a key evolutionary mechanism influencing gene regulation and trait development; however, how successive genome duplications reshape chromatin at the genome‐wide scale and thereby drive phenotypic innovation remains unclear. To dissect the effects of genome doubling on chromatin dynamics, gene expression, and associated trait differences, monoploid, diploid, and autotetraploid Brassica rapa L. ssp. pekinensis lines are generated with an identical genomic background and performed integrative analyses using ATAC‐seq, ChIP‐seq (H3K4me3, H3K27ac, H3K27me3), and RNA‐seq. By establishing this uniform ploidy series, nonlinear and stage‐specific chromatin and transcriptional reprogramming during autopolyploidization are revealed. Increased ploidy reprogrammed chromatin accessibility, characterized by reduced proximal and expanded distal regions, with effects particularly pronounced during the monoploid‐to‐diploid transition. Corresponding changes in H3K4me3 modifications near transcription start sites alter global gene expression. Numerous transcription factor genes are identified, of which BrGRF13 and BrARF11 are crucial regulators of leaf size and polarity during head development. Overall, this study elucidates the molecular basis by which ploidy variation drives chromatin remodeling and phenotypic divergence, providing new insights into how genome duplication shapes plant traits and informs polyploid crop improvement.