An OsWRKY11 gene, which encodes a transcription factor with the WRKY domain, was identified as one of the genes that was induced by both heat shock and drought stresses in seedlings of rice (Oryza sativa L.). To determine if overexpression of OsWRKY11 confers heat and drought tolerance, OsWRKY11 cDNA was fused to the promoter of HSP101 of rice and introduced into a rice cultivar Sasanishiki. Overexpression of OsWRKY11 was induced by heat treatment. After heat pretreatment, the transgenic lines showed significant heat and drought tolerance, as indicated by the slower leaf-wilting and less-impaired survival rate of green parts of plants. They also showed significant desiccation tolerance, as indicated by the slower water loss in detached leaves. Our results indicate that the OsWRKY11 gene plays a role in heat and drought stress response and tolerance, and might be useful for improvement of stress tolerance.

In the CMO-expressing rice plants, the localization of spinach CMO and of endogenous BADHs might be different and/or the catalytic activity of spinach CMO in rice plants might be lower than it is in spinach. These possibilities might explain the low levels of GB in the transgenic rice plants. It was concluded that CMO-expressing rice plants were not effective for accumulation of GB and improvement of productivity.

No abstract

A study was performed to examine whether or not betaine (glycinebetaine), a compatible solute, is accumulated in response to cold stress and is involved in mechanisms that protect plants from freezing injury. For this purpose, we used near‐isogenic lines of barley, with each line differing only in a single gene for the spring type of growth habit; the various lines were produced by back‐crosses to a recurrent cultivar of the winter type. The winter type of growth habit requires a low temperature for triggering of flower development (vernalization), whereas the spring type does not. Betaine was accumulated to five times the basal level over the course of 3 weeks at low temperature (5 °C) in the winter‐type cultivar and in a spring‐sh line having the sh gene for the spring‐type growth habit, but the level was only doubled in the spring‐Sh3 line, which carried the Sh3 gene for the spring‐type growth habit. Among near‐isogenic lines of the same cultivar, the levels of betaine accumulated in leaves at low temperature were well correlated with the percentages (on a dry weight basis) of green leaves that survived freezing injury (‐5 °C). This observation indicates the possibility, separate from the recognized role of betaine in the response to salinity and/or drought, that betaine accumulates in response to cold stress and that the accumulation of betaine during cold acclimation is associated to some extent with freezing tolerance in leaves of barley plants.

A linkage map of expressed sequence tag (EST)-based markers in radish (Raphanus sativus L.) was constructed using a low-cost and high-efficiency single-nucleotide polymorphism (SNP) genotyping method named multiplex polymerase chain reaction–mixed probe dot-blot analysis developed in this study. Seven hundred and forty-six SNP markers derived from EST sequences of R. sativus were assigned to nine linkage groups with a total length of 806.7 cM. By BLASTN, 726 markers were found to have homologous genes in Arabidopsis thaliana, and 72 syntenic regions, which have great potential for utilizing genomic information of the model species A. thaliana in basic and applied genetics of R. sativus, were identified. By construction and analysis of the genome structures of R. sativus based on the 24 genomic blocks within the Brassicaceae ancestral karyotype, 23 of the 24 genomic blocks were detected in the genome of R. sativus, and half of them were found to be triplicated. Comparison of the genome structure of R. sativus with those of the A, B, and C genomes of Brassica species and that of Sinapis alba L. revealed extensive chromosome homoeology among Brassiceae species, which would facilitate transfer of the genomic information from one Brassiceae species to another.

;The level of cis-unsaturated fatty acids in phosphatidylglycerol (PG) from rice leaves was genetically altered from 19.3% in the wild-type to 29.4 and 32.0% in T1 plants segregated with cDNAs for glycerol-3-phosphate acyltransferase of chloroplasts (GPAT; EC 2.3.1.15) from Arabidopsis (+AGPAT plant) and spinach (+SGPAT plant), respectively; and to 21.4% in a non-transformant segregated from +SGPAT plants (-SGPAT plant). In all these plants, O 2 evolution from leaves was similar at 25°°°°C and was impaired to a similar extent at 5 and 11°°°°C. However, in parallel with the levels of cis-unsaturated fatty acids in PG, +AGPAT and +SGPAT plants showed less impaired rates of O 2 evolution from leaves than the wild-type and -SGPAT plants at 14 and 17°°°°C. In agreement with this, the fresh weight of 14-day-old seedlings increased to 571± ± ± ±18, 591± ± ± ±23, 687± ± ± ±32 and 705± ± ± ±31 mg in the wild-type, -SGPAT, +AGPAT and +SGPAT plants, respectively, after 6 weeks at 17/14°°°°C (day/night). These results demonstrate the practical importance of the present technology with GPAT in improvement of the chilling sensitivity of crops.

Glycinebetaine is synthesized in plants by the two-step oxidation of choline, with betaine aldehyde as the intermediate. The reactions are catalyzed by choline monooxygenase and betaine aldehyde dehydrogenase. Rice plants, which do not accumulate glycinebetaine, possess a gene encoding betaine aldehyde dehydrogenase, whose activity is detectable at low levels. To evaluate the compatibility in rice of glycinebetaine on growth and tolerance to salt, cold and heat, we produced transgenic rice plants by introduction of a cDNA for betaine aldehyde dehydrogenase of barley, which is localized in peroxisomes unlike the chloroplast-specific localization of betaine aldehyde dehydrogenase in spinach and sugar beet. The transgenic rice plants converted high levels of exogenously applied betaine aldehyde (up to 10 mol m -3 ) to glycinebetaine more efficiently than did wild-type plants. The elevated level of glycinebetaine in transgenic plants conferred significant tolerance to salt, cold and heat stress. However, very high levels of glycinebetaine, resulting from conversion of applied betaine aldehyde to glycinebetaine or from exogenous application, inhibited increases in length of rice plants but not increases in dry weight. Our results suggested that the benefits of accumulation of glycinebetaine by rice plants might be considerable under high light conditions.

Exposure of 28-day-old rice seedlings for 6 days to 150 mm NaCl was found to induce drastic decreases in relative water contents, chlorophyll, and proteins in the leaves. This effect was largely prevened when before the exposure to NaCl the seedlings were treated for 4 days with 15 mm glycinebetaine. Although rice plants do not accumulate glycinebetaine endogenously, added glycinebetaine was found to be taken up by the roots and to accumulate in the leaves to reach a concentration of up to 5.0 μmol per gram fresh weight. The level is comparable with those of barley and wheat, which are well known glycinebetaine accumulators, under salt stress. The quantum yield of PSII was decreased by 27% under salt stress. This decrease was also largely prevented by glycinebetaine application.