Effect of phage XooG01 and flagella protein of Xanthomonas oryzae pv. oryzae on Xa genes expression in rice

Bacterial leaf blight (BLB) is caused by the phytopathogen Xanthomonas oryzae pv. oryzae (Xoo), a destructive disease that significantly threatens rice production. Controlling bacterial leaf blight on rice (Oryzae sativa) is important through the plant resistance approach, including pathogen-derived ligands such as flagella to induce plant resistance mechanisms, in addition to using lytic bacteriophage. This study investigated the interaction between the bacteriophage XooG01 and flagellar proteins from Xoo H02 on the expression of resistance genes in rice. Leaves were pre-treated with a mixture of the phage and bacterial cell surface appendages before pathogen inoculation, and gene expression was measured using semi-quantitative RT-PCR. The results revealed a paradoxical transcriptional response. While the expression of genes Xa10 and xa13 was significantly upregulated in treated leaves after pathogen challenge, the expression of the primary immune receptor Xa21 was, contrary to expectations, significantly decreased. The expression of Xa4 showed a slight, non-significant increase. This unexpected suppression of Xa21 suggests a phage-mediated interference in the host-pathogen recognition process, likely by the phage physically masking the flagellin elicitor from plant receptors. These findings reveal a complex tripartite interaction with critical implications for the design of future biocontrol strategies.