In Arabidopsis GCN containing protein complexes are

In Arabidopsis, GCN5-containing protein complexes are found to be involved in cell differentiation, leaf and floral organogenesis [[8], [9], [10]]. AtHAC1 has involvement with root elongation, flowering, fertility and de novo shoot regeneration [11,12]. AtHAM1 and AtHAM2 control flowering time by epigenetic modification of H4K5 acetylation on FLOWERING LOCUS C (FLC) and MADS-box affecting flowering genes 3/4 (MAF3/4) [13]. The mutant of SGF29a which encodes a subunit of GCN5 complex in Arabidopsis exhibits increased tolerance to salt stress in relative to the wild-type [14]. GCN5 and ADA2 (Alteration/deficiency in activation 2) could be recruited by CBF1 in Arabidopsis and positively regulate cold responsive genes during cold accumulation [15]. Wuschel-related homeobox gene (WOX11) regulates crown root meristem through the recruitment of ADA2-GCN5 complex in rice [16]. In addition, HATs also participate in photoreaction process [17] and ethylene signaling pathway [18]. B. distachyon has a close relationship with barley, wheat and other important food crops and becomes an excellent model plant for functional genomics of temperate cereals and forage grasses [19]. With the complete sequencings of B. distachyon genome [20], several gene families such as WRKY [21], bZIP [22] and AP2/EREBP [23] have been systematically studied. However, little has been done on the HAT superfamily in B. distachyon. Although the expression patterns of HATs under stress in another monocot plant rice [6] has been investigated, the identification and function of HATs in B. distachyon still need to be studied. That is because B. distachyon diverged from wheat 32–39 Myr ago, rice 40–53Myr ago, and sorghum 45–60Myr ago, which makes it a more ideal model system for wheat and bioenergy grass biology relative to rice. Secondly, the function of some homologs even with high similarity in cyclic amp function in the closely related species diverged during the evolution. Therefore, the results concluded from rice can't be completely consistent with that of B. distachyon. In this study, we firstly identified and characterized the HAT gene family in B. distachyon using systematic bioinformatics, expression profile and interaction analyses. Our results are very helpful for further function analysis of HAT genes in B. distachyon and its closely related monocot plants.
Materials and methods
Results
Discussion
Conclusions Eight HATs were identified from B. distachyon and grouped into four major families as in Arabidopsis and rice. The same number of HATs was identified in its closely related plants of rice, sorghum and maize. Collinearity and phylogenetic analysis of HAC proteins in the monocot and dicot plants showed that the HAC family may share two common ancestral genes before the divergence of monocot and dicot plants. However, HACs in dicot Arabidopsis evolved much faster than in monocot plants. Subcellular localization analysis showed that a majority of BdHATs were localized in the nucleus, implying that lysine acetylation by HATs occurs in histones but also in non-histone proteins located in other compartments such as cytoplasm. Expression analyses showed that BdHAG1 and all the BdHACs were highly expressed in caryopses of B. distachyon, BdHAG3 was significantly induced by four stresses we detected. Interestingly, the expression profiles of three BdHAC proteins (BdHAC1, BdHAC4 and BdHAC5) had obvious positive correlation in both our tested organs and stress treatments, indicating the functional redundancy of the three HAC proteins in B. distachyon, which was consistent with our speculation in the above that the HAC proteins in monocot group II shared a same ancestral gene prior to their divergence of these species. Functional interaction network analysis provided us some correlated genes with BdHATs. Importantly, one orthologs of the predicted interactive genes with HATs has been proved by experiments in rice and Arabidopsis. In short, our results could provide some insight in further functional identification of HAT genes in B. distachyon.