The glyoxalase pathway involving glyoxalase I (gly I) and glyoxalase II (gly II) enzymes is required for glutathione-based detoxification of methylglyoxal. We had earlier indicated the potential of gly I as a probable candidate gene in conferring salinity tolerance. We report here that overexpression of gly I + II together confers improved salinity tolerance, thus offering another effective strategy for manipulating stress tolerance in crop plants. We have overexpressed the gly II gene either alone in untransformed plants or with gly I transgenic background. Both types of these transgenic plants stably expressed the foreign protein, and the enzyme activity was also higher. Compared with nontransformants, several independent gly II transgenic lines showed improved capability for tolerating exposure to high methylglyoxal and NaCl concentration and were able to grow, flower, and set normal viable seeds under continuous salinity stress conditions. Importantly, the double transgenic lines always showed a better response than either of the single gene-transformed lines and WT plants under salinity stress. Ionic measurements revealed higher accumulation of Na ⁺ and K ⁺ in old leaves and negligible accumulation of Na ⁺ in seeds of transgenic lines as compared with the WT plants. Comparison of various growth parameters and seed production demonstrated that there is hardly any yield penalty in the double transgenics under nonstress conditions and that these plants suffered only 5% loss in total productivity when grown in 200 mM NaCl. These findings establish the potential of manipulation of the glyoxalase pathway for increased salinity tolerance without affecting yield in crop plants.

Many chemicals are critical for plant growth and development and play an important role in integrating various stress signals and controlling downstream stress responses by modulating gene expressi...

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.

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.