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Eight Saltol quantitative trait locus (QTL) linked simple sequence repeat (SSR) markers of rice (Oryza sativa L.) were used to study the polymorphism of this QTL in 142 diverse rice genotypes that comprised salt tolerant as well as sensitive genotypes. The SSR profiles of the eight markers generated 99 alleles including 20rare alleles and 16 null alleles. RM8094 showed the highest number (13) of alleles followed by RM3412 (12), RM562 (11), RM493 (9) and RM1287 (8) while as, RM10764 and RM10745 showed the lowest number (6) of alleles. Based on the highest number of alleles and PIC value (0.991), we identified RM8094 as suitable marker for discerning salt tolerant genotypes from the sensitive ones. Based upon the haplotype analysis using FL478 as a reference (salt tolerant genotypes containing Saltol QTL), we short listed 68 rice genotypes that may have at least one allele of FL478 haplotype. Further study may confirm that some of these genotypes might have Saltol QTL and can be used as alternative donors in salt tolerant rice breeding programmes.

DUF221 domain-containing genes (DDP genes) play important roles in developmental biology, hormone signalling transduction, and responses to abiotic stress. Therefore to understand their structural and evolutionary relationship, we did a genome-wide analysis of this important gene family in rice. Further, through comparative genomics, DDP genes from Oryza sativa subsp. (indica), nine different wild species of rice and Arabidopsis were also identified. We also found an expansion of the DDP gene families in rice and Arabidopsis which is due to the segmental duplication events in some of the gene family members. In general, a highly purifying selection was found acting on all the deduced paralogous and orthologous DDP gene pairs. The data from microarray and subsequent qRT-PCR analysis revealed that although several OsDDPs were differentially regulated under salinity stress, yet OsDDP6 was upregulated at all the developmental stages in salt tolerant rice genotype, FL478. Interestingly, OsDDP6 was found to be involved in proline metabolism pathway as indicated by protein network analysis. The diverse gene structures, varied transmembrane topologies and the differential expression patterns implied the functional diversity in DDP genes. Therefore, the comprehensive evolutionary analysis of DDP genes from different Oryza species and Arabidopsis performed in this study will provide the basis for further functional validation studies vis-à-vis DDP genes of rice and other plant species.

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