Plasmodiophora brassicae (P. brassicae) is a soil-born pathogen worldwide and can infect most cruciferous plants, which causes great yield decline and economic losses. It is not well known how microbial diversity and community composition change during P. brassicae infecting plant roots. Here, we employed a resistant and a susceptible pakchoi cultivar with and without inoculation with P. brassicae to analyze bacterial and fungal diversity using 16S rRNA V3-V4 and ITS_V1 regions, respectively. 16S rRNA V3-V4 and ITS_V1 regions were amplified and sequenced separately. Results revealed that both fungal and bacterial diversity increased, and composition was changed in the rhizosphere soil of the susceptible pakchoi compared with the resistant cultivar. In the four groups of R_mock, S_mock, R_10d, and S_10d, the most relatively abundant bacterium and fungus was Proteobacteria, accounting for 61.92%, 58.17%, 48.64%, and 50.00%, respectively, and Ascomycota, accounting for 75.11%, 63.69%, 72.10%, and 90.31%, respectively. A total of 9488 and 11,914 bacteria were observed uniquely in the rhizosphere soil of resistant and susceptible pakchoi, respectively, while only 80 and 103 fungi were observed uniquely in the correlated soil. LefSe analysis showed that 107 and 49 differentially abundant taxa were observed in bacteria and fungi. Overall, we concluded that different pakchoi cultivars affect microbial diversity and community composition, and microorganisms prefer to gather around the rhizosphere of susceptible pakchoi. These findings provide a new insight into plant–microorganism interactions.

Downy mildew caused by the obligate parasite Hyaloperonospora brassicae is a devastating disease for Brassica species. Infection of Hyaloperonospora brassicae often leads to yellow spots on leaves, which significantly impacts quality and yield of pakchoi. In the present study, we conducted a comparative transcriptome between the resistant and susceptible pakchoi cultivars in response to Hyaloperonospora brassicae infection. A total of 1073 disease-resistance-related differentially expressed genes were identified using a Venn diagram. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that these genes were mainly involved in plant−pathogen interaction, plant hormone signal transduction, and other photosynthesis-related metabolic processes. Analysis of the phytohormone content revealed that salicylic acid increased significantly in the resistant material after inoculation with Hyaloperonospora brassicae, whereas the contents of jasmonic acid, abscisic acid, and 1-aminocyclopropane-1-carboxylic acid decreased. Exogenous salicylic acid treatment also significantly upregulated Hyaloperonospora brassicae-induced genes, which further confirmed a crucial role of salicylic acid during pakchoi defense against Hyaloperonospora brassicae. Based on these findings, we suggest that the salicylic-acid-mediated signal transduction contributes to the resistance of pakchoi to downy mildew, and PAL1, ICS1, NPR1, PR1, PR5, WRKY70, WRKY33, CML43, CNGC9, and CDPK15 were involved in this responsive process. Our findings evidently contribute to revealing the molecular mechanism of pakchoi defense against Hyaloperonospora brassicae.

Background: The straw mushroom (Volvariella volvacea) is one of the important vegetables that is popular for its delicious taste. However, the straw mushroom is sensitive to low temperature, resulting in economic loss during transportation and storage. We obtained a novel straw mushroom strain, named VH3, via ultraviolet mutagenesis. Results: Our study revealed that VH3 exhibited high cold resistance compared to an ordinary straw mushroom cultivar, V23. We found that the electrolyte leakages of VH3 were always significantly lower than that of V23 treated with 4 °C for 0 h, 2 h,4 h, 8 h, 16 h, and 24 h. Before cold treatment (0 h), there were no difference of MDA contents, SOD activities, and CAT activities between VH3 and V23. At the late stage (8 h, 26 h, and 24 h) of cold treatment, the MDA contents of VH3 were lower while both the SOD and CAT activities were higher than those of V23. To investigate the potential mechanisms of VH3 cold resistance, we performed transcriptome sequencing to detect the transcriptome profiling of VH3 and V23 after 0 h and 4 h cold treatment. Transcriptome sequencing revealed that 111 differentially expressed genes (DEG) between V23 (0 h) and VH3 (0 h) (V23–0_vs_VH3–0), consisting 50 up-regulated and 61 down-regulated DEGs. A total of 117 DEGs were obtained between V23 (4 h) and VH3(4 h) (V23–4_vs_VH3–4), containing 94 up-regulated and 23 down-regulated DEGs. Among these DEGs, VVO_00021 and VVO_00017 were up-regulated while VVO_00003, VVO_00004, VVO_00010, and VVO_00030 were down-regulated in V23–0_vs_VH3–0 and VH3–4_vs_V23–4. KEGG and GO analysis revealed that the 6 DEGs were annotated to pathways related to cold stress. Besides, the GA3 content was also decreased in VH3. Conclusions: Collectively, our study first revealed that the increased cold resistance of VH3 might be caused by the expression change of VVO_00003, VVO_00004, VVO_00017, VVO_00021, and VVO_00030, and decreased GA₃.

Hypocotyl length is a critical determinant for the efficiency of mechanical harvesting in pakchoi production, but the knowledge on the molecular regulation of hypocotyl growth is very limited. Here, we report a spontaneous mutant of pakchoi, lhy7.1, and identified its characteristics. We found that it has an elongated hypocotyl phenotype compared to the wild type caused by the longitudinal growth of hypocotyl cells. Different light quality treatments, transcriptome, and proteomic analyses were performed to reveal the molecular mechanisms of hypocotyl elongation. The data showed that the hypocotyl length of lhy7.1 was significantly longer than that of WT under red, blue, and white lights but there was no significant difference under dark conditions. Furthermore, we used transcriptome and label-free proteome analyses to investigate differences in gene and protein expression levels between lhy7.1 and WT. At the transcript level, 4568 differentially expressed genes (DEGs) were identified, which were mainly enriched in “plant hormone signal transduction”, “photosynthesis”, “photosynthesis–antenna proteins”, and “carbon fixation in photosynthetic organisms” pathways. At the protein level, 1007 differentially expressed proteins (DEPs) were identified and were mainly enriched in photosynthesis-related pathways. The comprehensive transcriptome and proteome analyses revealed a regulatory network of hypocotyl elongation involving plant hormone signal transduction and photosynthesis-related pathways. The findings of this study help elucidate the regulatory mechanisms of hypocotyl elongation in lhy7.1.

Clubroot disease is a kind of soil-borne disease that seriously infects Brassica species. In this study, we collected 121 varieties of non-heading Chinese cabbages. In order to better understand the genetic variation and to screen suitable clubroot disease-resistant parental material, we re-sequenced them to examine the population genetic structure, population genetic diversity, population differentiation index, and selective sweep based on SNPs. The mapping rate with the reference genome was high, and data quality analysis revealed that the sequencing quality was good. The annotated data indicated that intronic and intergenic areas held the majority of SNPs and indels. Four subgroups of 121 non-heading Chinese cabbages were identified using principal component analysis, phylogenetic tree, and genetic structure analysis. An examination of genetic diversity revealed that while selfing may happen in subgroups C and D, heterozygosity may exist in subgroups A and B. In subgroup B, self-fertilization is not possible. There was a moderate degree of genetic differentiation between subgroups B and C (Fst = 0.0744347). For genes in certain sweep regions, we also ran GO enrichment and KEGG enrichment analysis. Two disease resistance-related genes, BraA01g042910.3.5C and BraA06g019360.3.5C, were examined. These findings will serve as a theoretical foundation for developing novel, clubroot disease-resistant types of non-heading Chinese cabbages.