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Background: Histone chaperones modulate chromatin architecture and hence play a pivotal role in epigenetic regulation of gene expression. In contrast to their animal and yeast counterparts, not much is known about plant histone chaperones. To gain insights into their functions in plants, we sought to identify histone chaperones from two model plant species and investigated their phylogeny, domain architecture and transcriptional profiles to establish correlation between their expression patterns and potential role in stress physiology and plant development. Results: Through comprehensive whole genome analyses of Arabidopsis and rice, we identified twenty-two and twenty-five genes encoding histone chaperones in these plants, respectively. These could be classified into seven different families, namely NAP, CAF1, SPT6, ASF1, HIRA, NASP, and FACT. Phylogenetic analyses of histone chaperones from diverse organisms including representative species from each of the major plant groups, yeast and human indicated functional divergence in NAP and CAF1C in plants. For the largest histone chaperone family, NAP, phylogenetic reconstruction suggested the presence of two distinct groups in plants, possibly with differing histone preferences. Further, to comment upon their physiological roles in plants, we analyzed their expression at different developmental stages, across various plant tissues, and under biotic and abiotic stress conditions using pre-existing microarray and qRT-PCR. We found tight transcriptional regulation of some histone chaperone genes during development in both Arabidopsis and rice, suggesting that they may play a role in genetic reprogramming associated with the developmental process. Besides, we found significant differential expression of a few histone chaperones under various biotic and abiotic stresses pointing towards their potential function in stress response. Conclusions: Taken together, our findings shed light onto the possible evolutionary trajectory of plant histone chaperones and present novel prospects about their physiological roles. Considering that the developmental process and stress response require altered expression of a large array of genes, our results suggest that some plant histone chaperones may serve a regulatory role by controlling the expression of genes associated with these vital processes, possibly via modulating chromatin dynamics at the corresponding genetic loci. [ABSTRACT FROM AUTHOR]

Background: In Arabidopsis thaliana (L.) Heynh and Oryza sativa L., a large number of genes encode proteins of unknown functions, whose characterization still remains one of the major challenges. With an aim to characterize these unknown proteins having defined features (PDFs) in plants, we have chosen to work on proteins having a cystathionine β-synthase (CBS) domain. CBS domain as such has no defined function(s) but plays a regulatory role for many enzymes and thus helps in maintaining the intracellular redox balance. Its function as sensor of cellular energy has also been widely suggested. Results: Our analysis has identified 34 CBS domain containing proteins (CDCPs) in Arabidopsis and 59 in Oryza. In most of these proteins, CBS domain coexists with other functional domain(s), which may indicate towards their probable functions. In order to investigate the role(s) of these CDCPs, we have carried out their detailed analysis in whole genomes of Arabidopsis and Oryza, including their classification, nomenclature, sequence analysis, domain analysis, chromosomal locations, phylogenetic relationships and their expression patterns using public databases (MPSS database and microarray data). We have found that the transcript levels of some members of this family are altered in response to various stresses such as salinity, drought, cold, high temperature, UV, wounding and genotoxic stress, in both root and shoot tissues. This data would be helpful in exploring the so far obscure functions of CBS domain and CBS domain-containing proteins in plant stress responses. Conclusion: We have identified, classified and suggested the nomenclature of CDCPs in Arabidopsis and Oryza. A comprehensive analysis of expression patterns for CDCPs using the already existing transcriptome profiles and MPSS database reveals that a few CDCPs may have an important role in stress response/tolerance and development in plants, which needs to be validated further through functional genomics. [ABSTRACT FROM AUTHOR]

Background: Rice genome sequencing projects have generated remarkable amount of information about genes and genome architecture having tremendous potential to be utilized in both basic and applied research. Success in transgenics is paving the way for preparing a road map of functional genomics which is expected to correlate action of a gene to a trait in cellular and organismal context. However, the lack of a simple and efficient method for transformation and regeneration is a major constraint for such studies in this important cereal crop., Results: In the present study, we have developed an easy, rapid and highly efficient transformation and regeneration protocol using mature seeds as explants and found its successful applicability to a choice of elite indica rice genotypes. We have optimized various steps of transformation and standardized different components of the regeneration medium including growth hormones and the gelling agent. The modified regeneration medium triggers production of large number of shoots from smaller number of calli and promotes their faster growth, hence significantly advantageous over the existing protocols where the regeneration step requires maximum time. Using this protocol, significantly higher transformation efficiency (up to 46%) and regeneration frequency (up to 92% for the untransformed calli and 59% for the transformed calli) were achieved for the four tested cultivars. We have used this protocol to produce hundreds of independent transgenic lines of different indica rice genotypes. Upon maturity, these transgenic lines were fertile thereby indicating that faster regeneration during tissue culture did not affect their reproductive potential., Conclusions: This speedy, yet less labor-intensive, protocol overcomes major limitations associated with genetic manipulation in rice. Moreover, our protocol uses mature seeds as the explant, which can easily be obtained in quantity throughout the year and kept viable for a long time. Such an easy, efficient and generalized protocol has the potential to be a major tool for crop improvement and gene-function studies on the model monocot plant rice.