Syed Tariq Shah

Isolation and expression profiling of GhNAC transcription factor genes in cotton (Gossypium hirsutum L.) during leaf senescence and in response to stresses.

NAC (NAM, ATAF, and CUC) is a plant-specific transcription factor family with diverse roles in plant development and stress regulation. In this report, stress-responsive NAC genes (GhNAC8-GhNAC17) isolated from cotton (Gossypium hirsutum L.) were characterised in the context of leaf senescence and stress tolerance. The characterisation of NAC genes during leaf senescence has not yet been reported for cotton. Based on the sequence characterisation, these GhNACs could be classified into three groups belonging to three known NAC sub-families. Their predicted amino acid sequences exhibited similarities to NAC genes from other plant species. Senescent leaves were the sites of maximum expression for all GhNAC genes except GhNAC10 and GhNAC13, which showed maximum expression in fibres, collected from 25 days post anthesis (DPA) plants. The ten GhNAC genes displayed differential expression patterns and levels during natural and induced leaf senescence. Quantitative RT-PCR and promoter analyses suggest that these genes are induced by ABA, ethylene, drought, salinity, cold, heat, and other hormonal treatments. These results support a role for cotton GhNAC genes in transcriptional regulation of leaf senescence, stress tolerance and other developmental stages of cotton.

Molecular cloning and functional analysis of NAC family genes associated with leaf senescence and stresses in Gossypium hirsutum L.

The NAC domain genes encode a large family of plant-specific transcription factors that play diverse roles in plant development and stress regulation. In this study, a total of 60 full-length putative NAC genes were isolated from Gossypium hirsutum L. Based on their phylogeny, all GhNAC genes were clustered into seven distinct subfamilies, which exhibit functional similarity. Similarly, a phylogenetic tree for GhNAC genes and their motif showed close resemblance among the subfamilies. The isolated 60 full-length GhNAC genes were located on 13 different chromosomes of D sub-genome. Majority of the NACs showed specific temporal and spatial expression patterns in tissue-specific (fibers, cotyledon leaf, mature leaf, stem, root and flower) studies based on qRT-PCR analyses. Furthermore, the roles of GhNAC genes were monitored using qRT-PCR during leaf senescence and following treatment with ethylene, abscisic acid, gibberellic acid and drought or salinity. This first comprehensive study of GhNAC family elucidates the essential role of these genes in cotton development and in response to various stresses. This study lays fundamental foundations for future research and development in cotton genome.

Effect of IAA on in vitro growth and colonization of Nostoc in plant roots.

Nostoc is widely known for its ability to fix atmospheric nitrogen and the establishment of symbiotic relationship with a wide range of plants from various taxonomic groups. Several strains of Nostoc produce phytohormones that promote growth of its plant partners. Nostoc OS-1 was therefore selected for study because of the presence of putative ipdC gene that encodes a key enzyme to produce Indole-3-acetic acid (IAA). The results indicated that both cellular and released IAA was found high with increasing incubation time and reached to a peak value (i.e., 21 pmol mg-1ch-a) on the third week as determined by UPLC-ESI-MS/MS. Also the Nostoc OS-1 strain efficiently colonized the roots and promoted the growth of rice as well as wheat under axenic conditions and induced ipdC gene that suggested the possible involvement of IAA in these phenotypes. To confirm the impact of IAA on root colonization efficiency and plant promoting phenotypes of Nostoc OS-1, an ipdC knockout mutant was generated by homologous recombinant method. The amount of releasing IAA, in vitro growth, root colonization, and plant promoting efficiency of the ipdC knockout mutant was observed significantly lower than wild type strain under axenic conditions. Importantly, these phenotypes were restored to wild-type levels when the ipdC knockout mutant was complemented with wild type ipdC gene. These results together suggested that ipdC and/or synthesized IAA of Nostoc OS-1 is required for its efficient root colonization and plant promoting activity.

Efficient In Vitro Regeneration of Sugarcane (Saccharum Officinarum L.) from Bud Explants

ABSTRACT The regeneration potential of the economically important plant Saccharum officinarum (Sugarcane) was investigated. Callus induction and shoot regeneration along with somatic embryogenesis were induced from bud explants incubated on Murashige and Skoog (MS)-medium supplemented with different plant growth regulators (PGRs) and white sugar. The best callus induction (83.33%) was observed on explants incubated on MS-medium plus 1.0 mg·l−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 4.0 mg·l−1 2,4-D (70%) after 6 weeks of culture. Other combinations (BA, IBA, IAA, NAA and GA3) of PGRs were less effective than 2,4-D. It was observed that lower concentrations of 2,4-D induced somatic embryos in bud explants of Saccharum officinarum, whereas higher concentrations induced non-embryogenic calli. Subsequent sub-culturing of calli onto MS-medium supplemented with BA (6-benzyladenine) induced shoot organogenesis. Highest shoot induction (98%) was recorded for 2.0 mg·l−1 after 3 weeks of culture. With this concentration of BA, maximum number of (178) shoots per explant were recorded, and, when the shoots were transferred to elongation medium, the longest shoots (9.4 cm) were recorded. However, 5.6 cm long shoots were also recorded with 3.0 mg·l−1 zeatin. No root induction hormones were used for rooting. The elongated shoots started rooting upon maturation. A maximum rooting (84%), number of roots/shoot (21) and mean root length of 5.0 cm were observed on medium containing 2.0 mg·l−1 BA along with 1.0 mg·l−1 GA3. The regenerated plantlets were successfully acclimated in field conditions.

Antioxidant activity influenced by in vivo and in vitro mutagenesis in sugarcane ( Saccharum officinarum L.)

The antioxidant potential (1,1-diphenyl-2-picrylhydrazyl (DPPHo)-scavenging activity) of in vitro regenerated and induced mutant sugarcane (Saccharum officinarum L.) was investigated. Efficient callus induction and shoot regeneration were induced in bud explants when incubated on Murashige and Skoog (MS) medium supplemented with different plant growth regulators (PGRs). Best callogenesis was observed on MS-medium supplemented with 3 mg L -1 2,4 dichlorophenoxyacetic acid (2,4 D) and on ½ MS medium with 2 mg L -1 2,4 D after 30-days of culture. Almost 85% shoot organogenesis was observed on MS-medium supplemented with 2 mg L -1 6-benzyladenine (BA) and 0.5 mg L -1 gibberellic acid (GA3) within 30 days. Optimum percentage rooting (89%), were obtained for 2 mg L -1 of BA alone. Mother plant setts were irradiated with 60Co mutagen source. Assay of antioxidant activity of in vitro and in vivo grown tissues was evaluated as gross parameter of medicinal efficacy. Significantly higher antioxidant activity (60%) in in vitro regenerated sugarcane was observed as compared to induced mutant (57%) and mother plant (53%). Key words: Saccharum officinarum, in vitro regeneration, induced mutation, antioxidant.