The PcMYB44‐mediated miR397‐PcLACs module regulates defence‐induced lignification in pear resistance to fungal disease

Abstract

Diseases caused by Alternaria alternata and Botryosphaeria dothidea diminish pear yield and quality, and restrict the pear agricultural industry. Lignification is a conserved mechanism for plant resistance against pathogen invasion. The regulatory mechanisms underlying defence‐induced lignification in pear in response to fungal pathogen infection remain unknown. In this study, analysis of lignification level and lignin content in pear revealed that A. alternata and B. dothidea induced lignification, and transcriptomics showed that lignin biosynthesis was affected. To explore whether laccases (LACs) mediated by miR397 regulate lignification in pear, we investigated the role of PcmiR397 in repressing the expression of PcLACs using 5′‐RNA ligase‐mediated‐RACE and co‐transformation in tobacco. Opposite expression patterns for PcmiR397 and PcLAC target genes were observed in pear in response to pathogens. Transient transformation in pear demonstrated that silencing PcmiR397 and overexpressing a single PcLAC enhanced resistance to pathogens via lignin synthesis. To further reveal the mechanism underpinning the PcMIR397 response of pear to pathogens, the PcMIR397 promoter was analysed, and pMIR397‐1039 was found to be inhibited by pathogen infection. The transcription factor PcMYB44 was up‐regulated, and it bound to the PcMIR397 promoter and inhibited transcription following pathogen infection. The results demonstrate the role of PcmiR397‐PcLACs in broad‐spectrum resistance to fungal disease, and the potential role of PcMYB44 involved in the miR397‐PcLAC module in regulating defence‐induced lignification. The findings provide valuable candidate gene resources and guidance for molecular breeding to improve resistance to fungal disease in pear.

More or Less: Recent Advances in Lignin Accumulation and Regulation in Horticultural Crops

“…Furthermore, lignin deposition can diffuse pathogens by restricting the access of fungal enzymes and toxins into the host plants and preventing the movement of nutrients from hosts to invaders [2]. Lignification in pear results from plant resistance against diseases caused by Alternaria alternata and Botryosphaeria dothidea, and the PcMYB44-mediated PcmiR397-PcLACs module may be involved in the process of defense-induced lignification [59]. Leaf-spot-infected leaves had increased transcription of lignin biosynthesis genes and enhanced lignin accumulation in an important medicinal plant, Withania somnifera [60].…”

Contribution of the LAC Genes in Fruit Quality Attributes of the Fruit-Bearing Plants: A Comprehensive Review

“…This upregulation is correlated with an increase in the activity of the transcription factors activated by PbMYB26, which directly bind to the promoters of the PbLAC4-like gene and activate its expression [11]. In addition to transcriptional regulation, LAC gene expression is also post-transcriptionally regulated by microRNAs (miRNAs) [5]. MiRNAs are short RNA molecules that can bind to complementary sequences in mRNA and inhibit their translation or promote mRNA degradation.…”

“…Laccases catalyze the oxidation of phenolic compounds to quinones, which can immobilize pathogens by crosslinking their cell wall components or by producing toxic compounds. In addition to their antifungal and antibacterial properties, laccases also contribute to the browning of fruits during storage and processing, which can affect their shelf-life and nutritional quality [5,31].…”

“…Additionally, laccase enzymes are involved in the biosynthesis of pigments such as proanthocyanidins (PAs), which give fruits their characteristic colors [4]. LAC genes are also involved in the defense mechanisms of plants against pathogens and environmental stresses [5]. Hence, the LAC genes are essential for the growth, development, and ripening of fruits in plants, as well as for their structural integrity and response to environmental factors [5,6].…”

“…LAC genes are also involved in the defense mechanisms of plants against pathogens and environmental stresses [5]. Hence, the LAC genes are essential for the growth, development, and ripening of fruits in plants, as well as for their structural integrity and response to environmental factors [5,6]. Laccases are enzymes that play a key role in lignin biosynthesis, which is the process by which plants make cell walls and provide them with structural support.…”