Expression of ascorbate peroxidase and glutathione reductase in roots of rice seedlings in response to NaCl and H2O2

The accumulation of H2O2 by NaCl was observed in the roots of rice seedlings. Treatment with NaCl caused an increase in the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) and the expression of OsAPX and OsGR in rice roots. Exogenously applied H2O2 also enhanced the activities of APX and GR and the expression of OsAPX and OsGR in rice roots. The accumulation of H2O2 in rice roots in response to NaCl was inhibited by the NADPH oxidase inhibitors, diphenyleneiodonium chloride (DPI) and imidazole (IMD). However, DPI, IMD, and dimethylthiourea, a H2O2 trap, did not reduce NaCl-enhanced activities of APX and GR and expression of OsAPX and OsGR. It appears that H2O2 is not involved in the regulation of NaCl-induced APX and GR activities and OsAPX and OsGR expression in rice roots.

Source: Journal of plant physiology (2005) vol. 162, p. 291-299

Over-expression of ζ glutathione S-transferase in transgenic rice enhances germination and growth at low temperature

To develop a rice cultivar that would be suitable for direct-seedingcultivation in cooler temperate regions, we generated transgenic rice plants inwhich a rice encoding a -class glutathioneS-transferase (GST) under the control of a maize ubiquitinpromoter. GSTs have been suggested to be responsible for tolerance to variousstresses such as cold, salt and drought by detoxification of xenobioticcompounds and reactive oxygen species. A total of 87 R0 transgenicrice plants harboring a chimeric GST gene were generatedusing Agrobacterium mediated transformation. ThreeR2 lines homozygous for the transgene were assayed for GST activityand had higher GST and glutathione peroxidase activities thannon-transformants.Seedlings of the transgenic lines demonstrated greatly enhanced germination andgrowth rates at low temperature grown under submergence. The GST transgeniclines should be useful for breeding rice cultivars suitable for direct-seedingcultivation in cooler temperate regions.

Source: Molecular Breeding (2002) vol. 9, p. 93-101

Optimising the tissue culture conditions for high efficiency transformation of indica rice

Establishment of high efficiency Agrobacterium-mediated transformation techniques has greatly accelerated the widespread application of transformation in japonica rice. However, transformation in indica rice remains difficult. In this study, we identify two new media for subculture and differentiation, the two major steps in the tissue culture process for transformation. These media were tested using four cultivars representing very different germplasms of indica rice. The results show that the new media significantly improved the growth rate and quality of the calli, and also increased the differentiation rate for all four cultivars tested. Use of these modified media in transformation experiments also greatly improved the transformation efficiency of all four indica cultivars.

Source: Plant Cell Rep. (2005) vol. 23, p. 540-547

Variability in expression of insecticidal Cry1Ab gene in Indica Basmati rice

The expression of an insecticidal gene cry1Ab, under three different promoters was studied in leaves, stem and panicles to determine organ-specificity in Basmati rice. Enhanced resistance against two Lepidopteran insects, stem borer (Scirpophaga incertulas) and leaf folder (Cnaphalocrocis medinalis) was observed. The result of western hybridization and insect bioassays demonstrated that all these promoters express the cry1Ab gene at similar levels in leaves and panicles. The cry1Ab gene was expressed in stems at 0.05% of the total protein under the control of the PEPC promoter alone or in combination with the pollen-specific promoter. On the other hand it was expressed at 0.15% under the control of the ubiquitin promoter. Southern blot hybridization of these plants indicated integration of the complete plant transcriptional unit at multiple insertion sites. These results demonstrated that a specific promoter could be used to limit the expression of cry1Ab gene in the desired parts of Basmati rice plants.

Source: Euphytica (2002) vol. 128, p. 121-128

Over-expression of the bacterial nhaA gene in rice enhances salt and drought tolerance

The Escherichia coli nhaA gene encodes a Na+/H+ antiporter, which plays a critical role in ion homeostasis. We transferred a bacterial nhaA gene into rice (Oryza sativa L. ssp. japonica) and detected high expression in the transgenic rice. The germination rate, growth, and average yield per plant of the transgenic lines were better than those of control lines under salt or drought stress. Moreover, the sodium and proline content of the transgenic lines under salt or drought stress was also higher than in control lines, implying that nhaA over-expression enhances osmoregulation by activating the biosynthesis of proline. Tolerance to both salt and drought was compared between transgenic rice over-expressing nhaA and that over-expressing Arabidopsis δ-OAT encoding ornithine-8-aminotransferase. The transgenic plants with nhaA grew better than those with δ-OAT at high salinity, while the opposite was true for drought stress.

Source: Plant science (2005) vol. 168, p. 297-302