Weiyi Chen

Pear black spot disease is a serious fungal disease during pear production; salicylic acid is a core signaling molecule that regulates the expression of plant disease resistance genes. To elucidate the intrinsic association between salicylic acid-induced resistance to pear black spot disease and lignin biosynthesis, in vitro plantlets of two pear cultivars, ‘Xinli No.7’ and ‘Xueqing’, were employed as experimental materials. After 60 h SA pretreatment, the leaves were inoculated with the pathogen Alternaria alternata. Leaf samples were harvested at 0, 8, 16, 24, and 48 h post-inoculation to determine phenylalanine ammonia-lyase activity, quantify lignin content, and analyze the transcript levels of genes involved in lignin synthesis. The results demonstrated that, relative to the untreated control group, SA treatment significantly enhanced phenylalanine ammonia-lyase activity and promoted lignin accumulation in both ‘Xinli No.7’ and ‘Xueqing’. Moreover, multiple key genes associated with lignin biosynthesis—including PbrPAL1, Pbr4CL1, PbrCOMT, PbrCCoAOMT, PbrCAD, and PbrPOD—were markedly upregulated, with their expression levels increasing by 3.5–15 fold. Transcript profiles of PbrHCT1, PbrHCT4, and PbrC3H1 exhibited cultivar-specific divergence between the two varieties. Notably, the susceptible cultivar ‘Xueqing’ displayed a distinct lag phase and attenuated response in the expression of all lignin-related genes compared with the other cultivar. This study provides reference for green prevention and sustainable development of pear.

Pear is an important originate fruiter in China, ranking first in the world in terms of cultivation area and yield. However, it is susceptible to infection by Alternaria alternata (A. alternata), resulting in a reduction of approximately 30% in yield. While both lignin and salicylic acid (SA) are recognized as key components of plant immune responses, the molecular mechanisms connecting these pathways remain poorly understood. Here, we have discovered a nuclear localization transcription activator PbrMYB14 in pears, whose expression can be induced by exogenous SA and A. alternata. Overexpression of PbrMYB14 significantly increased lignin and SA content in pears, making them more resistant to A. alternata, and the relative lesion area decreased by 68.95% compared with WT plants. By analyzing the transcriptome of PbrMYB14-overexpressing plants, the lignin synthesis gene Pbr4CL1 and SA synthesis gene PbrPAL1 regulated by PbrMYB14 were screened and identified. Through yeast one-hybrid (Y1H) and a Dual-Luciferase assay (LUC), it was confirmed that PbrMYB14 positively regulates the expression of Pbr4CL1 and PbrPAL1 genes. Our results suggest that PbrMYB14 links lignin resistance and SA resistance in pears, providing valuable information for future genetic breeding research on pear disease resistance.