Possible Role of Common bean (Phaseolus vulgaris L.) Histone deacetylase6 in Development and Cold Stress Response

Histone deacetylases (HDACs) are important regulators of chromatin structure and function. HDACs have been found to play key roles in plant developmental processes and also respond to environmental cues. For example, the Arabidopsis HDA6 has been shown to regulate transcription of ribosomal RNA and plays a role in cold acclimation. Despite its essential role in plants, HDA6 is yet to be validated in common bean. In this study, we cloned and sequenced HDA6 from common bean cultivar Sierra, a resistant genotype to Uromyces appendiculatus (rust race-53). To validate expression of the HDA6 at different developmental stages, and during cold stress, we used the quantitative real-time PCR. Analysis of the HDA6 amino acid sequence revealed very high similarity with homologues in model species, with highly conserved domains suggesting a critical role of this gene in planta. Our finding showed up-regulation of HDA6 in common bean with age (seedling >flowering >maturity). Spatial distribution analysis revealed more HDA6 transcripts in flowers and pods. Further validation of recombinant HDA6 protein by western blot using specific antibodies detected a 60 kDa protein. Interestingly, the transcripts of HDA6 are up-regulated in response to cold stress. To our knowledge, this is the first report suggesting a crucial role of HDA6 in common bean growth and development and also appears to be involved in the cold-response pathway. These findings would help in elucidating the functions of HDA6 in common bean and eventually help in understanding regulatory pathways controlled by HDA6.