LESION SIMULATING DISEASE 3 regulates disease resistance via fine-tuning histone acetylation in cassava.

Bacterial blight seriously affects the growth and production of cassava (Manihot esculenta Crantz), but disease resistance genes and the underlying molecular mechanism remain unknown. In this study, we found that LESION SIMULATING DISEASE 3 (MeLSD3) is essential for disease resistance in cassava. MeLSD3 physically interacts with SIRTUIN 1 (MeSRT1), inhibiting MeSRT1-mediated deacetylation modification at the acetylation of histone 3 at K9 (H3K9Ac). This leads to increased H3K9Ac levels and transcriptional activation of SUPPRESSOR OF BIR1 (SOBIR1) and FLAGELLIN-SENSITIVE2 (FLS2) in pattern-triggered immunity, resulting in immune responses in cassava. When MeLSD3 was silenced, the release of MeSRT1 directly decreased H3K9Ac levels and inhibited the transcription of SOBIR1 and FLS2, leading to decreased disease resistance. Notably, DELLA protein GIBBERELLIC ACID INSENSITIVE 1 (MeGAI1) also interacted with MeLSD3, which enhanced the interaction between MeLSD3 and MeSRT1 and further strengthened the inhibition of MeSRT1-mediated deacetylation modification at H3K9Ac of defense genes. In summary, this study illustrates the mechanism by which MeLSD3 interacts with MeSRT1 and MeGAI1, thereby mediating the level of H3K9Ac and the transcription of defense genes and immune responses in cassava.