Fungi represent an important source of bioactive secondary metabolites (SMs), which have wide applications in many fields, including medicine, agriculture, human health, and many other industries. The genes involved in SM biosynthesis are usually clustered adjacent to each other into a region known as a biosynthetic gene cluster (BGC). The recent advent of a diversity of genetic and genomic technologies has facilitated the identification of many cryptic or uncharacterized BGCs and their associated SMs. However, there are still many challenges that hamper the broader exploration of industrially important secondary metabolites. The recent advanced CRISPR/Cas system has revolutionized fungal genetic engineering and enabled the discovery of novel bioactive compounds. In this review, we firstly introduce fungal BGCs and their relationships with associated SMs, followed by a brief summary of the conventional strategies for fungal genetic engineering. Next, we introduce a range of state-of-the-art CRISPR/Cas-based tools that have been developed and review recent applications of these methods in fungi for research on the biosynthesis of SMs. Finally, the challenges and limitations of these CRISPR/Cas-based systems are discussed and directions for future research are proposed in order to expand their applications and improve efficiency for fungal genetic engineering.

The plant cell wall is dynamically modified during host–pathogen interactions and acts as a crucial factor controlling plant immunity. In the context of recently revised models of plant primary cell walls (PCWs), pectin is considered to be important in determining the mechanical properties of PCWs. A secondary cell wall is present in some cell types and lignin is normally present and acts to strengthen wall rigidity. In this review, we summarize the recent advances in understanding cell-wall-mediated defense responses against pathogens in Brassica napus L. (B. napus). A major part of this response involves pectin and lignin, and these two major cell wall components contribute greatly to immune responses in B. napus. Crosstalk between pectin and lignin metabolism has been detected in B. napus upon pathogen infection, suggesting a synergistic action of pectin and lignin metabolism in regulating cell wall integrity as well as wall-mediated immunity. The transcriptional regulation of cell-wall-mediated immunity in B. napus along with that in Arabidopsis is discussed, and directions for future work are proposed for a better understanding of wall-mediated plant immunity in B. napus.

Pectin methylesterase inhibitors (PMEIs) modulate the status of pectin methylesterification by inhibiting the activity of pectin methylesterase (PME). Recent advances indicate PMEIs play an important role in regulating plant cell wall properties and defense responses. In this study, a genome-wide analysis of PMEI gene family in Brassica napus (B. napus) was conducted and the expression patterns of PMEI genes in response to Sclerotinia sclerotiorum (S. sclerotiorum) was investigated. A total of 190 PMEI proteins were identified from the genome of B. napus. Chromosomal location, gene structure and properties of the PMEI family were analyzed, and these features were compared with Arabidopsis thaliana (A. thaliana). A total of 123 syntenic ortholog pairs were detected from BnPMEI family by synteny analysis. Results showed the expansion of BnPMEI genes was likely predominately from whole-genome duplication (WGD) or segmental duplications. Multiple cis-elements related to plant growth and development, environmental stress responses, hormone responses were detected in the promoters of BnPMEI genes, implying they were regulated by both internal and external factors. Furthermore, expression analysis of transcriptome data combined with quantitative RT-PCR (qRT-PCR) validation identified several candidates that were strongly responsive to S. sclerotiorum infection. These BnPMEI genes are candidates for manipulation to breed novel and improved genotypes that are more resistant to sclerotinia stem rot (SSR). Extensive interactions were detected among 30 BnPMEI proteins, forming complex protein-protein interaction networks. Besides, 48 BnPMEIs showed interactions with other proteins including a range of cell wall structure-related enzymes. This study provides new insights into the evolution and function of PMEIs in B. napus and lays a foundation for breeding novel genotypes for crop improvement.