Genetic diversity analysis of specialty glutinous and low-amylose rice (Oryza sativa L.) landraces of Assam based on Wx locus and microsatellite diversity

The sticky rice of Assam is traditionally classified as bora (glutinous) and chokuwa (semi-glutinous) basedon their stickiness after cooking. The Waxy (Wx) gene encodes for granule-bound starch synthase (GBSS)that controls the synthesis of amylose, which is a key determinant of rice end-use quality attributes. In thisreport, we analysed the level of variation in grain quality traits in a collection of bora and chokuwacultivars, and examined the nucleotide diversity at the Wx locus of selected rice accessions to identify thepossible cause of low-amylose in these rice cultivar groups. The Wx gene sequencing from 24 bora andchokuwa cultivars revealed several nucleotide variations that can explain the variation in the amylosephenotypes. The nucleotide polymorphisms in the downstream intron regions were similar to those reportedin Bangladeshi Beruin cultivars. Among the Wx polymorphisms, the CTn microsatellite in exon 1 and G/TSNP in intron 1 (G/T-Int1) should be considered for marker assisted breeding involving bora cultivars. TheWx gene tree, classified the bora accessions possessing the G/T-Int1 SNP as japonicas. However, clusteranalysis using microsatellite markers classified the bora and chokuwa cultivars as indica, and intermediateof indica-aus. The findings of this study supplemented our understanding on the evolution of the Wx geneunder human selection. The results will assist plant breeders to effectively improve the bora and chokuwalandraces.

A revisit of the mode of interaction of small transcription inhibitors with genomic DNA.

One class of small molecules with therapeutic potential for treatment of cancer functions as transcription inhibitors via interaction with double-stranded DNA. Majority of the studies of the interaction with DNA have so far been reported under conditions nonexistent in vivo. Inside the cell, DNA is present in the nucleus as a complex with proteins known as chromatin. For the last few years we have been studying the interaction of these DNA-binding small molecules at the chromatin level with emphasis on the drug-induced structural alterations in chromatin. Our studies have shown that at the chromatin level these molecules could be classified in two broad categories: single-binding and dual-binding molecules. Single-binding molecules access only DNA in the chromatin, while the dual-binding molecules could bind to both DNA and the associated histone(s). Structural effects of the DNA-binding molecules upon chromatin in light of the above broad categories and the associated biological implications of the two types of binding are discussed.