Cut flower ornamental kale (Brassica oleracea var. acephala) is a biennial cultivar, which completes a sexual reproductive generation in two years. Isolated microspore culture (IMC) can accelerate plant homozygosity instead of self-pollinations. However, the application of IMC in cut flower ornamental kale was rare since its low rate of embryogenesis. It is proved that histone acetylation might affect the gene expression in microspores and led to the transformation of microspores from pollen development pathway to embryogenesis. In this paper, microspores, derived from three varieties of cut flower ornamental kale, Crane Bicolor (CB), Crane Pink (CP) and Crane Feather Queen (CFQ), were treated with histone deacetylation inhibitor (HDACI) trichostatin A (TSA). Results revealed that the appropriate concentration of TSA was 10 nM for CB with obtaining 5.39 embryos per bud, while for CP and CFQ was 5 nM with acquiring 10.89 and 16.99 embryos per bud, respectively. TSA treatment also reduced the embryonic mortality, of which 10 nM TSA treatments CB was the optimal and the embryonic mortality decreased to 25.01%. The double haploid (DH) proportion of regenerated plants reached 37.3%. These results contribute to improving the technology for IMC in cut flower ornamental kale.

Leafy head formation is one of the most important characteristics of Chinese cabbage, and the process is regulated by a series of genes and environmental factors. In this study, a non-heading short leaf mutant slm was identified from an ethyl methane sulfonate mutagenesis (EMS) population of the heading Chinese cabbage line FT. The most significant phenotypic characteristics of slm was shortening leaves and increasing leaf numbers, which led to failure to form a leafy head. Genetic analysis showed that a single recessive gene Brslm was responsible for the mutant phenotype. Mutmap analysis suggested that Brslm was located on chromosome A07, and four candidate genes were predicted. KASP analysis demonstrated that BraA07g039390.3C was the target gene of the candidates. BraA07g039390.3C is a homologous to Arabidopsis CLV1 encoding receptor kinase with an extracellular leucine-rich domain. Sequencing analysis revealed that a single SNP from G to A occurred in 904th nucleotide of Brclv1, which resulted in the change of the 302nd amino acid from Asp to Asn. The SNP was co-segregated with the mutant phenotype in F₂ individuals and located on the conserved domains. These results indicated that BrCLV1 was the mutant gene for slm which led to shortening leaves and increasing leaf numbers, disrupting the leafy heading formation in FT. These findings contribute to revealing the BrCLV1 function in leafy head formation in Chinese cabbage.

Chinese cabbage is one of the major vegetable crops in northern Asia. Its leaves are the major organ for photosynthesis and production, and leaf color directly influences its yield and quality. Here, we obtained a pale green mutant pgm3. This mutant line was derived from EMS mutagenesis of Chinese cabbage DH line FT. pgm3 exhibited chlorosis and etiolation, delayed growth, reduced photosynthetic pigment content and net photosynthetic rates, and impaired development of the chloroplast inner membrane system. Genetic analysis revealed that the pale green phenotype was controlled by a single recessive nuclear gene, Brpgm3. Mutmap analysis indicated that Brpgm3 is located on a 13.9 Mb region in A03. Within this region, a single SNP (A03: 7194530) with an SNP-index of 1, located in BraA03g015750.3C (BrClpC1), was identified from 40 differential SNPs. KASP genotyping demonstrated that the SNP co-segregated with the pale green phenotype in the F₂ population. Sanger sequencing confirmed a G-to-A SNP in exon 4 of BrClpC1, which resulted in an amino acid substitution from S to G. Furthermore, multiple sequence alignment of homologs from 28 species demonstrated that this mutated residue is highly conserved. BrClpC1 was predominantly expressed in leaves and exhibited the highest transcript abundance among the nine members of the Class I Clp gene family in Brassica rapa. This is the first report identifying ClpC1 in Brassica crops. Our results not only confirmed BrClpC1 as a strong candidate gene for the pale green mutant of Chinese cabbage, but also highlighted BrClpC1 as a target for chloroplast biology research in Brassica crops.

To elucidate the cooperative regulatory mechanisms underlying Paraburkholderia sp. GD17-mediated salt tolerance in cucumber plants. Hydroponically grown cucumber plants were inoculated with GD17 and subsequently subjected to NaCl treatment. Physiological, biochemical parameters, as well as gene expression profiles, were comprehensively analyzed. GD17 inoculation significantly improved plant growth, developmental performance, and salinity tolerance. Under salt stress, GD17-inoculated plants exhibited higher leaf nutrient contents compared to non-inoculated controls, particularly an elevated K⁺/Na⁺ ratio, which was closely associated with the upregulated expression of Na⁺ extrusion-related genes. A substantial increase in proline content and the corresponding biosynthesis-related gene expression indicated that enhanced osmoprotectant synthesis played a critical role in GD17-conferred salt tolerance. Phytohormone levels and their signaling-related gene expression were also significantly upregulated in GD17-inoculated plants under salt stress. Moreover, transcription factor gene expression was markedly increased in GD17-treated plants following salt exposure. GD17 inoculation alleviated salt-induced photosynthetic inhibition, as demonstrated by improved photosynthetic efficiency and reduced suppression of photosynthesis-related gene expression. Transcriptional profiling further revealed that starch degradation, photorespiration, and the pentose phosphate pathway were crucial for GD17-mediated salt tolerance. Reduced oxidative damage, driven by enhanced antioxidative activity, further contributed to the observed protective mechanisms. This study demonstrates that the application of Paraburkholderia sp. GD17 concurrently enhances cucumber growth and salinity tolerance, effectively resolving the trade-off between growth and defense. Multi-level analyses provided comprehensive mechanistic insights into these synergistic effects.

Leafy head formation is a critical agronomic trait that determines the yield and quality of Chinese cabbage (Brassica rapa), involving complex morphological transitions. While BEL1-like homeodomain (BLH) transcription factors regulate development, their specific roles in heading remain elusive. To systematically identify the BraBLH gene family and elucidate its expression networks and regulatory functions during leafy head formation, a total of 36 BraBLH genes were identified. The phylogenetic analysis revealed that Brassica rapa had a specific clade (Group II). A high-resolution spatiotemporal expression framework for the BraBLH family was constructed. Subsequently, comparative transcriptomics of heading, non-heading, and GA₃-treated heading plants highlighted multiple differentially expressed BraBLH genes, suggesting that this gene family may contribute to the regulation of leafy head formation in Chinese cabbage. Subsequently, a high-resolution spatiotemporal expression framework for the BraBLH family was constructed. Within this framework, BraBLH5 emerged as a pivotal node integrating GA signaling, peaking during the rosette stage to initiate heading. In contrast, a distinct negative module (BraBLH9/26) was significantly upregulated in the non-heading line. Spatial profiling further revealed functional compartmentalization within the family, where specific members maintained shoot apical meristem identity, whereas others drove inner leaf expansion and incurvature. Furthermore, subcellular localization analysis confirmed that BraBLH5 was localized to the nucleus. Ultimately, this systems-level study elucidates a transcriptome-driven framework for heading, highlighting a GA-mediated BraBLH5 mechanism and providing valuable candidates for Brassica functional genomics.