Generating high temperature tolerant transgenic plants: Achievements and challenges

Production of plants tolerant to high temperature stress is of immense significance in the light of global warming and climate change. Plant cells respond to high temperature stress by re-programming their genetic machinery for survival and reproduction. High temperature tolerance in transgenic plants has largely been achieved either by over-expressing heat shock protein genes or by altering levels of heat shock factors that regulate expression of heat shock and non-heat shock genes. Apart from heat shock factors, over-expression of other trans-acting factors like DREB2A, bZIP28 and WRKY proteins has proven useful in imparting high temperature tolerance. Besides these, elevating the genetic levels of proteins involved in osmotic adjustment, reactive oxygen species removal, saturation of membrane-associated lipids, photosynthetic reactions, production of polyamines and protein biosynthesis process have yielded positive results in equipping transgenic plants with high temperature tolerance. Cyclic nucleotide gated calcium channel proteins that regulate calcium influxes across the cell membrane have recently been shown to be the key players in induction of high temperature tolerance. The involvement of calmodulins and kinases in activation of heat shock factors has been implicated as an important event in governing high temperature tolerance. Unfilled gaps limiting the production of high temperature tolerant transgenic plants for field level cultivation are discussed.

Forced expression of Mdmyb10, a myb transcription factor gene from apple, enhances tolerance to osmotic stress in transgenic Arabidopsis

In plants, anthocyanins often appear at specific developmental stages, but are also induced by a number of environmental factors. The coordinated expression of genes encoding the anthocyanin biosynthetic pathway enzymes is controlled at the transcriptional level usually by an R2R3Myb transcription factor. However, little is known about the effects of R2R3-Myb on plant resistance to environmental stresses. In this study, we introduced an R2R3Myb transcription factor gene Mdmyb10, a regulatory gene of anthocyanin biosynthesis in apple fruit, into Arabidopsis and analyzed its function to osmotic stress in transgenic plants. Under high osmotic stress, the Mdmyb10 over-expressing plants exhibited growth better than wild-type plants. The elevated tolerance of the transgenic plants to osmotic stress was confirmed by the changes of flavonoids, chlorophyll, malondialdehyde and proline contents. These results preliminarily showed that the Mdmyb10 can possibly be used to enhance the high osmotic-tolerant ability of plants.