Intermittent drought adversely impacts monogenic resistance of rice to the blast pathogen Magnaporthe oryzae and is associated with alteration in histone acetylation

Abstract

Aims: Climate change is affecting rainfall patterns causing intermittent drought stress to rainfed rice. It is poorly understood how intermittent drought impacts the blast of rice incited by Magnaporthe oryzae. Methods: The impact of intermittent drought on virulence factors of Magnaporthe oryzae and defense responses in blast resistant (C101A51 and Tetep), susceptible (HR-12) and drought-tolerant (Vandana) rice cultivars was analyzed in stress overlapped conditions. Transcript accumulation of rice defense genes, histone acetyltransferases (OsHATs) and pathogenesis-associated genes of M. oryzae was recorded and histone acetylation at H3K9 and H4K5 was assessed through western blotting. Results: Predisposition to intermittent drought favored blast development in all rice cultivars. Higher blast resistance in C101A51 is linked to enhanced histone acetylation at H3K9 compared to Tetep. However, intermittent drought predisposition caused partial breakdown of blast resistance due to reduced OsHAT activities that led to reduced histone acetylation at H3K9. ABA signaling was predominant in drought predisposed and M. oryzae challenged plants compared to SA signaling in only M. oryzae challenged plants. Interestingly, pathogenesis-associated genes (chitin synthases, chitin deacetylases, appressorium formation) of M. oryzae were highly expressed in the drought predisposed plants compared to only M. oryzae challenged plants. Conclusions: Intermittent drought induces vulnerability of rice to blast disease. Vulnerability of rice to the pathogen in drought predisposed conditions is attributed to reduced activities of the histone acetyltransferases (OsHATs), masking of SA-signaling by ABA-signaling as well as enhanced activities of pathogenesis-associated genes in M. oryzae. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.