Neelam Yadav

MYB transcription factor genes as regulators for plant responses: an overview

Regulation of gene expression at the level of transcription controls many crucial biological processes. Transcription factors (TFs) play a great role in controlling cellular processes and MYB TF family is large and involved in controlling various processes like responses to biotic and abiotic stresses, development, differentiation, metabolism, defense etc. Here, we review MYB TFs with particular emphasis on their role in controlling different biological processes. This will provide valuable insights in understanding regulatory networks and associated functions to develop strategies for crop improvement.

High frequency plant regeneration from desiccated calli of indica rice (Oryza Sativa l.)

An efficient and reproducible protocol is required to achieve high frequency transformation from transformed calli. We report here high frequency plant regeneration from mature seed derived embryogenic calli of two recalcitrant indica rice cultivars HKR-46 and HKR-126 after partial desiccation treatment. Embryogenic and nodular callus was initiated on MS basal medium supplemented with 2.5 mg l -1 2,4-D, 500 mg l -1 proline, 500 mg l -1 casein hydrolysate, 30 g l -1 sucrose and 2.5 g l -1 gelrite. Several media with different combinations of growth regulators were tried. Maximum shoot regeneration frequency (63%) was observed in partially desiccated calli for 48 h in cv. HKR 46 and 82.1 per cent in cv. HKR-126 on the MS modified medium supplemented with 2 mg l -1 kinetin + 0.5 mg l -1 NAA + 30 gl -1 sucrose + 6 g l -1 gelrite followed by in the medium supplemented with 1 mgl -1 2ip + 30 g l -1 sucrose + 6 g l -1 gelrite (61% in cv. HKR-46 and 79.2 % in cv. HKR-126). Highly significant regeneration differences were observed in partially desiccated calli (48 h) in comparison to non-dehydrated (0 h desiccation) calli. Shoot regeneration frequency increased from 1.2 to 5.6 fold after 48 h of desiccation in both the cultivars on different regeneration media. Shoot regeneration frequency declined at 72 h desiccation treatment as compared to 48 h treatment. Well-developed plantlets were hardened and transferred to the green house. Key words: Plant regeneration; indica rice; mature embryo; partial desiccation. African Journal of Biotechnology Vol.3(5) 2004: 256-259

Sequence-related amplified polymorphism (SRAP) molecular marker system and its applications in crop improvement

Plant biotechnology has great potential for improving target traits in crops. This can be achieved by the production of transgenic crops and marker-assisted breeding. Marker-assisted breeding has gained momentum in recent times since it does not need biosafety regulations. Several kind of molecular markers are available for use in crop breeding, such as restriction fragment length polymorphism, microsatellites, sequence characterized amplified region, sequence-tagged site, inter-simple sequence repeat amplification, amplified fragment length polymorphism and single nucleotide polymorphism. Sequence-related amplified polymorphism is a novel molecular marker system which is based on open reading frames (ORFs) developed from genome sequence data of Arabidopsis. It provides a unique combination of forward and reverse primers which can be selected arbitrarily giving a large number of primer combinations. Since this is an ORF-based marker system, it targets functional genes and has potential for their application in crop breeding. This marker system was first used and demonstrated by Li and Quiros in Brassica oleracea in 2001, and since then there have been several reports in different plant species ranging from field crops to tree species for assessing genetic diversity, mapping and tagging of genes, hybrid identification and sex determination. This review provides an overview of SRAP markers and their applications in crop improvement.