HDA19-mediated deacetylation of histone H3.3 at lysines 27 and 36 regulates plant sensitivity to salt stress.
TL;DR
It is demonstrated that H3.3K27/K36 diacetylation, modulated by HDA19, drives LEA protein accumulation and enables plants to withstand environmental stress, revealing a core mechanism of plant stress resilience.
Abstract
Plants survive extreme environments through rapid chromatin reprogramming, yet the epigenetic marks that confer stress resilience remain poorly understood. Histone deacetylase HDA19 is a key epigenetic regulator in Arabidopsis, and hda19-deficient mutants display tolerance to multiple abiotic stresses, including drought, heat, and salinity. Using lysine acetylome profiling, we identified a noncanonical K27/K36 diacetylation mark on histone H3.3, among nine H3 variants, as a specific substrate of HDA19. Under salinity stress, this mark decreased in wild-type plants but increased in hda19 mutants, while other known H3 modifications were similarly affected in both genotypes. Mimicking constitutive diacetylation of H3.3K27/K36 through lysine-to-glutamine substitutions promoted accumulation of stress-responsive late embryogenesis abundant (LEA) proteins and conferred salinity tolerance in seedlings, phenocopying hda19 mutants. Furthermore, generating the lea7-1/lea29-1/rab18-1 triple mutant abolished hda19-dependent salinity tolerance, confirming the LEA proteins' role downstream of HDA19. Our findings demonstrate that H3.3K27/K36 diacetylation, modulated by HDA19, drives LEA protein accumulation and enables plants to withstand environmental stress, revealing a core mechanism of plant stress resilience.