Using transfer DNA (T-DNA) with functions of gene trap and gene knockout and activation tagging, a mutant population containing 55,000 lines was generated. Approximately 81% of this population carries 1-2 T-DNA copies per line, and the retrotransposon Tos17 was mostly inactive in this population during tissue culture. A total of 11,992 flanking sequence tags (FSTs) have been obtained and assigned to the rice genome. T-DNA was preferentially ( approximately 80%) integrated into genic regions. A total of 19,000 FSTs pooled from this and another T-DNA tagged population were analyzed and compared with 18,000 FSTs from a Tos17 tagged population. There was difference in preference for integrations into genic, coding, and flanking regions, as well as repetitive sequences and centromeric regions, between T-DNA and Tos17; however, T-DNA integration was more evenly distributed in the rice genome than Tos17. Our T-DNA contains an enhancer octamer next to the left border, expression of genes within genetics distances of 12.5 kb was enhanced. For example, the normal height of a severe dwarf mutant, with its gibberellin 2-oxidase (GA2ox) gene being activated by T-DNA, was restored upon GA treatment, indicating GA2ox was one of the key enzymes regulating the endogenous level of GA. Our T-DNA also contains a promoterless GUS gene next to the right border. GUS activity screening facilitated identification of genes responsive to various stresses and those regulated temporally and spatially in large scale with high frequency. Our mutant population offers a highly valuable resource for high throughput rice functional analyses using both forward and reverse genetic approaches.

With the completion of the rice genome sequencing project, the next major challenge is the largescale determination of gene function. As an important crop and a model organism, rice provides major insights into gene functions important for crop growth or production. Phenomics with detailed information about tagged populations provides a good tool for functional genomics analysis. By a T-DNA insertional mutagenesis approach, we have generated a rice mutant population containing 55,000 promoter trap and gene activation or knockout lines. Approximately 20,000 of these lines have known integration sites. The T0 and T1 plants were grown in net ''houses'' for two cropping seasons each year since 2003, with the mutant phenotypes recorded. Detailed data describing growth and development of these plants, in 11 categories and 65 subcategories, over the entire four-month growing season are available in a searchable database, along with the genetic segregation information and flanking sequence data. With the detailed data from more than 20,000 T1 lines and 12 plants per line, we estimated the mutation rates of the T1 population, as well the frequency of the dominant T0 mutants. The correlations among different mutation phenotypes are also calculated. Together, the information about mutant lines, their integration sites, and the phenotypes make this collection, the Taiwan Rice Insertion Mutants (TRIM), a good resource for rice phenomics study. Ten T2 seeds per line can be distributed to researchers upon request.

Background The impact of climate change on insect resistance genes is elusive. Hence, we investigated the responses of rice near-isogenic lines (NILs) that carry resistance genes against brown planthopper (BPH) under different environmental conditions. Results We tested these NILs under three environmental settings (the atmospheric temperature with corresponding carbon dioxide at the ambient, year 2050 and year 2100) based on the Intergovernmental Panel on Climate Change prediction. Comparing between different environments, two of nine NILs that carried a single BPH-resistant gene maintained their resistance under the environmental changes, whereas two of three NILs showed gene pyramiding with two maintained BPH resistance genes despite the environmental changes. In addition, two NILs (NIL-BPH17 and NIL-BPH20) were examined in their antibiosis and antixenosis effects under these environmental changes. BPH showed different responses to these two NILs, where the inhibitory effect of NIL-BPH17 on the BPH growth and development was unaffected, while NIL-BPH20 may have lost its resistance during the environmental changes. Conclusion Our results indicate that BPH resistance genes could be affected by climate change. NIL-BPH17 has a strong inhibitory effect on BPH feeding on phloem and would be unaffected by environmental changes, while NIL-BPH20 would lose its ability during the environmental changes.

Wild relatives of rice in the genus Oryza (composed of 24 species with 11 different genome types) have been significantly contributing to the varietal improvement of rice (Oryza sativa). More than 4000 accessions of wild rice species are available and they are regarded as a “genetic reservoir” for further rice improvement. DNA markers are essential tools in genetic analysis and breeding. To date, genome-wide marker sets for wild rice species have not been well established and this is one of the major difficulties for the efficient use of wild germplasm. Here, we developed 541 genome-wide InDel markers for the discrimination of alleles between the cultivated species O. sativa and the other seven AA-genome species by positional multiple sequence alignments among five AA-genome species with four rice varieties. The newly developed markers were tested by PCR-agarose gel analysis of 24 accessions from eight AA genome species (three accessions per species) along with two representative cultivars (O. sativa subsp. indica cv. IR24 and subsp. japonica cv. Nipponbare). Marker polymorphism was validated for 475 markers. The number of polymorphic markers between IR24 and each species (three accessions) ranged from 338 (versus O. rufipogon) to 416 (versus O. longistaminata) and the values in comparison with Nipponbare ranged from 179 (versus O. glaberrima) to 323 (versus O. glumaepatula). These marker sets will be useful for genetic studies and use of the AA-genome wild rice species.

Brown planthopper (BPH), a monophagous phloem feeder, consumes a large amount of photoassimilates in rice and causes wilting. A near-isogenic line ‘TNG71-Bph45’ was developed from the Oryza sativa japonica variety ‘Tainung 71 (TNG71) carrying a dominant BPH-resistance locus derived from Oryza nivara (IRGC 102165) near the centromere of chromosome 4. We compared the NIL (TNG71-Bph45) and the recurrent parent to explore how the Bph45 gene confers BPH resistance. We found that TNG71-Bph45 is less attractive to BPH at least partially because it produces less limonene. Chiral analysis revealed that the major form of limonene in both rice lines was the L-form. However, both L- and D-limonene attracted BPH when applied exogenously to TNG71-Bph45 rice. The transcript amounts of limonene synthase were significantly higher in TNG71 than in TNG71-Bph45 and were induced by BPH infestation only in the former. Introgression of the Bph45 gene into another japonica variety, Tainan 11, also resulted in a low limonene content. Moreover, several dominantly acting BPH resistance genes introduced into the BPH-sensitive IR24 line compromised its limonene-producing ability and concurrently decreased its attractiveness to BPH. These observations suggest that reducing limonene production may be a common resistance strategy against BPH in rice.