Plastid-expressed choline monooxygenase gene improves salt and drought tolerance through accumulation of glycine betaine in tobacco

Abstract

Glycine betaine (GlyBet), a quaternary ammonium compound, functions as an osmoprotectant in many organisms including plants. Previous research has shown that over-expression of enzymes for GlyBet biosynthesis in transgenic plants improved abiotic stress tolerance, but so far no study on the effects of plastid-expression of choline monooxygenase, the enzyme that catalyzes the conversion of choline into betaine aldehyde, has been reported. In the present study, tobacco (Nicotiana tabacum L. cv Wisconsin 38) plants were transformed with a gene for choline monooxygenase (BvCMO) from beet (Beta vulgaris) via plastid genetic engineering. Transplastomic plants constitutively expressing BvCMO under the control of the ribosomal RNA operon promoter and a synthetic T7 gene G10 leader were able to accumulate GlyBet in leaves, roots and seeds, and exhibited improved tolerance to toxic level of choline and to salt/drought stress when compared to wild type plants. Transplastomic plants also demonstrated higher net photosynthetic rate and apparent quantum yield of photosynthesis in the presence of 150 mM NaCl. Salt stress caused no significant change on the maximal efficiency of PSII photochemistry (Fv/Fm) in both wild type and transplastomic plants, but a decrease in the actual efficiency of PSII (PhiPSII) was observed, and such a decrease was much greater in wild type plants. Our results demonstrate the feasibility of improving salt and drought tolerance in plants through plastid transformation with BvCMO gene.

Genome-wide analysis of drought induced gene expression changes in flax (Linum usitatissimum)

“…77 Lipid transfer proteins involved in the deposition of cuticular wax that are important in drought tolerance 78 are also found to be upregulated in our study. It has been reported that mono-oxygenases are highly upregulated 79,80 during drought stress, but our data for the expression of mono-oxygenase is different and shows that this gene is downregulated in both shoot and root. Since T-397 is moderately tolerant to drought, raising the possibility that other genes except mono-oxygenases are involved to impart drought tolerant attributes.…”

Molecular Breeding for Enhancing Abiotic Stress Tolerance Using Halophytes

“…Transplastomic tobacco plants overexpressing BvCMO gene exhibited increased tolerance to salt and drought stress. Accumulation of GlyBet in transplastomic plants enhances the net photosynthetic rate and apparent quantum yield of photosynthesis under salt stress condition [80].…”

A phytocyanin-related early nodulin-like gene, BcBCP1, cloned from Boea crassifolia enhances osmotic tolerance in transgenic tobacco

“…Plants can respond and adapt to water stress by altering their cellular metabolism and invoking various defense mechanisms (Bohnert et al, 1995). A number of genes that respond to drought stress have been reported and confirmed to have functions in improving resistance to drought stress in plants through transgenic research, including osmoprotecants (Hayashi et al, 1997;Holmstrom et al, 1996;Taji et al, 2002;Yamada et al, 2005;Zhang et al, 2008), late embryogenesis abundant proteins (Lal et al, 2008;Xu et al, 1996), chaperones (Castiglioni et al, 2008), detoxification enzymes (McKersie et al, 1996;Miao et al, 2006) (that probably function by protecting cells from dehydration, and those which regulate gene expression and signal transduction in the stress response such as transcriptional factors (Oh et al, 2005;Pino et al, 2007)) and protein kinases (Xing et al, 2007;Xu et al, 2007). These results demonstrate that plants may improve drought stress through multiple pathways.…”