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Broad-spectrum resistance is highly preferred in crop breeding programmes. Previously, we have reported the identification of the broad-spectrum resistance-Digu 1 (bsr-d1) allele from rice Digu. The bsr-d1 allele prevents activation of Bsr-d1 expression by Magnaporthe oryzae infection and degradation of H 2 O 2 by peroxidases, leading to resistance to M. oryzae. However, it remains unknown whether defence pathways other than H 2 O 2 burst and peroxidases contribute to the bsr-d1-mediated immunity.Blast resistance was determined in rice leaves by spray and punch inoculations. Target genes of OsMYB30 were identified by one-hybrid assays in yeast and electrophoretic mobility shift assay. Lignin content was measured by phloroglucinol-HCl staining, and acetyl bromide and thioacidolysis methods.Here, we report the involvement of the OsMYB30 gene in bsr-d1-mediated blast resistance. Expression of OsMYB30 was induced during M. oryzae infection or when Bsr-d1 was knocked out or downregulated, as occurs in bsr-d1 plants upon infection. We further found that OsMYB30 bound to and activated the promoters of 4-coumarate:coenzyme A ligase genes (Os4CL3 and Os4CL5) resulting in accumulation of lignin subunits G and S. This action led to obvious thickening of sclerenchyma cells near the epidermis, inhibiting M. oryzae penetration at the early stage of infection.Our study revealed novel components required for bsr-d1-mediated resistance and penetration-dependent immunity, and advanced our understanding of broad-spectrum disease resistance.

SummaryRust fungi are devastating plant pathogens and cause a large economic impact on wheat production worldwide. To overcome this rapid loss of resistance in varieties, we generated stable transgenic wheat plants expressing short interfering RNAs (siRNAs) targeting potentially vital genes of Puccinia striiformis f. sp. tritici (Pst). Protein kinase A (PKA) has been proved to play important roles in regulating the virulence of phytopathogenic fungi. PsCPK1, a PKA catalytic subunit gene from Pst, is highly induced at the early infection stage of Pst. The instantaneous silencing of PsCPK1 by barley stripe mosaic virus (BSMV)‐mediated host‐induced gene silencing (HIGS) results in a significant reduction in the length of infection hyphae and disease phenotype. These results indicate that PsCPK1 is an important pathogenicity factor by regulating Pst growth and development. Two transgenic lines expressing the RNA interference (RNAi) construct in a normally susceptible wheat cultivar displayed high levels of stable and consistent resistance to Pst throughout the T3 to T4 generations. The presence of the interfering RNAs in transgenic wheat plants was confirmed by northern blotting, and these RNAs were found to efficiently down‐regulate PsCPK1 expression in wheat. This study addresses important aspects for the development of fungal‐derived resistance through the expression of silencing constructs in host plants as a powerful strategy to control cereal rust diseases.

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