Brajesh Singh

Translation initiation in plants: roles and implications beyond protein synthesis

Protein synthesis is a ubiquitous and essential process in all organisms, including plants. It is primarily regulated at translation initiation stage which is mediated through a number of translation initiation factors (eIFs). It is now becoming more apparent that in addition to synthesis of proteins, eIFs also regulate various aspects of plant development and their interaction with environment. Translation initiation factors, such as eIF3, eIF4A, eIF4E, eIF4G, and eIF5A affect different processes during vegetative and reproductive growth like embryogenesis, xylogenesis, flowering, sporogenesis, pollen germination, etc. On the contrary, eIF1A, eIF2, eIF4, and eIF5A are associated with interaction of plants with different abiotic stresses, such as high temperature, salinity, oxidative stress, etc. Similarly, eIF4E and eIF4G have roles in interaction with many viruses. Therefore, the translation initiation factors are important candidates for improving plant performance and adaptation. A large number of genes encoding eIFs can functionally be validated and utilized through genetic engineering approaches for better adaptability and performance of plants by inhibiting/minimizing or increasing expression of desired eIF(s).

Key players associated with tuberization in potato: potential candidates for genetic engineering

Abstract Tuberization in potato (Solanum tuberosum L.) is a complex biological phenomenon which is affected by several environmental cues, genetic factors and plant nutrition. Understanding the regulation of tuber induction is essential to devise strategies to improve tuber yield and quality. It is well established that short-day photoperiods promote tuberization, whereas long days and high-temperatures inhibit or delay tuberization. Worldwide research on this complex biological process has yielded information on the important bio-molecules (proteins, RNAs, plant growth regulators) associated with the tuberization process in potato. Key proteins involved in the regulation of tuberization include StSP6A, POTH1, StBEL5, StPHYB, StCONSTANS, Sucrose transporter StSUT4, StSP5G, etc. Biomolecules that become transported from “source to sink” have also been suggested to be important signaling candidates regulating the tuberization process in potatos. Four molecules, namely StSP6A protein, StBEL5 RNA, miR172 and GAs, have been found to be the main candidates acting as mobile signals for tuberization. These biomolecules can be manipulated (overexpressed/inhibited) for improving the tuberization in commercial varieties/cultivars of potato. In this review, information about the genes/proteins and their mechanism of action associated with the tuberization process is discussed.

Microarray analysis of gene expression patterns in the leaf during potato tuberization in the potato somatic hybrid Solanum tuberosum and Solanum etuberosum

Genes involved in photoassimilate partitioning and changes in hormonal balance are important for potato tuberization. In the present study, we investigated gene expression patterns in the tuber-bearing potato somatic hybrid (E1-3) and control non-tuberous wild species Solanum etuberosum (Etb) by microarray. Plants were grown under controlled conditions and leaves were collected at eight tuber developmental stages for microarray analysis. A t-test analysis identified a total of 468 genes (94 up-regulated and 374 down-regulated) that were statistically significant (p ≤ 0.05) and differentially expressed in E1-3 and Etb. Gene Ontology (GO) characterization of the 468 genes revealed that 145 were annotated and 323 were of unknown function. Further, these 145 genes were grouped based on GO biological processes followed by molecular function and (or) PGSC description into 15 gene sets, namely (1) transport, (2) metabolic process, (3) biological process, (4) photosynthesis, (5) oxidation-reduction, (6) transcription, (7) translation, (8) binding, (9) protein phosphorylation, (10) protein folding, (11) ubiquitin-dependent protein catabolic process, (12) RNA processing, (13) negative regulation of protein, (14) methylation, and (15) mitosis. RT-PCR analysis of 10 selected highly significant genes (p ≤ 0.01) confirmed the microarray results. Overall, we show that candidate genes induced in leaves of E1-3 were implicated in tuberization processes such as transport, carbohydrate metabolism, phytohormones, and transcription/translation/binding functions. Hence, our results provide an insight into the candidate genes induced in leaf tissues during tuberization in E1-3.

Potential of Indian potatoes for the management of hyperglycemia

Potatoes are less favoured by health conscious people due to the notion that it has high glycaemic index. Anti-hyperglycemic and antioxidative potential of Indian potato cultivars were evaluated with the aim to remove the misconception. Glycaemic index was measured indirectly through estimating resistant starch, amylose content and activity of α-amylase and α-glucosidase inhibitors from cooked tubers of 46 Indian potato cultivars. The α-glucosidase inhibitory activity ranged from 0 to 52.8% and was observed only in 14 cultivars, viz., Kufri Anand, Kufri Arun, Kufri Khasigaro, Kufri Kuber, Kufri Kundan, Kufri Muthu, Kufri Naveen, Kufri Neela, Kufri Pushkar, Kufri Red, Kufri Sadabahar, Kufri Safed, Kufri Sutlej and Kufri Swarna. α-amylase inhibitory activity was found only in cultivar Kufri Frysona (20.5%). Resistant starch content ranged from 1.22 to 1.93 mg/100 mg DW with highest value in Kufri Garima (1.93 mg/100 mg DW). Amylose content ranged from 10.8 to 27.6 mg/100 mg DW and was the maximum in processing cultivar Kufri Chipsona-3 (27.6 mg/100 mg DW). The highest activities of α-glucosidase inhibitors along with considerable resistant starch content was observed in cultivars, viz. Kufri Kuber, Kufri Khasigaro, Kufri Muthu, Kufri Naveen and Kufri Pushkar. Therefore, these potato cultivars can be used as speciality potatoes as these attributes have potential to prevent hyperglycemia helping manage the incidence of type II diabetes.

Antimicrobial Activity of Potato Starch-Based Active Biodegradable Nanocomposite Films

Food-borne pathogens such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) create a lot of problems worldwide and are a major concern of food producers and consumers. To protect the food from spoilage due to these bacteria, antimicrobial packaging is one of the most promising active packaging systems. Environmental concerns associated with plastic waste emphasized the development of packaging films from natural polymers such as starch. Therefore, in the present study, potato starch-based biodegradable and antimicrobial nanocomposite films were prepared with constant concentration of zinc oxide nanoparticles using casting method. Films were prepared using three antimicrobial agents, cinnamon oil, clove oil, and potassium sorbate and were tested against four microbes, S. aureus, E. coli, Salmonella typhi (S. typhi), and Campylobacter jejuni (C. jejuni). The films prepared with clove oil were most effective against S. aureus (22–100% inhibition), those prepared with cinnamon oil were effective against C. jejuni (19–22% inhibition) and growth of E. coli was inhibited (33–40% inhibition) to maximum extent by potassium sorbate incorporated films. However, for complete inhibition of C. jejuni and E. coli, higher concentrations of cinnamon oil and potassium sorbate are required. Increasing concentration of antimicrobial agents decreased the tensile strength of the films. Tensile strength decreased up to 13% in cinnamon oil films, 23% in clove oil films and up to 34% in potassium sorbate incorporated films. Based on the results, it can be concluded that cinnamon oil is a better antimicrobial agent due to its least effect on tensile strength and also due to its antibacterial effect against the three bacteria.

Effect of Elevated Temperature on In Vitro Microtuberization of Potato Genotypes with Different Thermotolerance Levels

Effect of Elevated Temperature on In Vitro Microtuberization of Potato Genotypes with Different Thermotolerance Levels Extension of potato cultivation to tropical areas has been constrained by the thermosensitivity of most cultivars which require low temperature during induction of tuber formation and their subsequent development. Development of culivars for heat tolerance requires robust phenotyping methods for evaluating germplasm which is generally maintained as in vitro plant cultures. Microtuber production behaviour of five potato genotypes with contrasting themotolerance levels was studied to develop an in vitro assay system for screening potato genotypes for tolerance to high temperatures. Significant differences were observed with respect to tuber number, tuber weight and plant weight in all the genotypes at ambient (18°C) and elevated temperature (25°C). Kufri Himalini and CP4054 produced highest tuber number at 18°C and 24°C respectively. Although plant weight increased with an increase in temperature in all genotypes, total biomass increased only in tolerant genotypes. Heat tolerant genotypes exhibited comparable tuberization at both the temperatures whereas tuber formation was reduced in heat sensitive genotypes at elevated temperature. All genotypes formed micro tubers in vitro but only thermotolerant genotypes formed tubers in soil at elevated temperature, suggesting that mixotropic culture media overcome the effect of high temperature in the inhibition of tuberization indicating the need to use culture media devoid of hormones for developing a reliable in vitro assay system.

Socio-economic feasibility of potato cultivation in Andhra Pradesh, India.

The potato processing industry has developed quickly during the past decade in India, and the demand for processing grade potato tubers has increased accordingly. As a consequence, potato market prices have dramatically risen, particularly in the southern states, where production is still limited. The potential for developing the production in these non-traditional areas has been demonstrated. Agronomical and socio-economic constraints need, however, to be better identified and addressed. The International Potato Centre (CIP) and the ICAR-Central Potato Research Institute (ICAR-CPRI), Shimla, have realized a joint survey to analyse the socio-economic factors determining the feasibility and profitability of potato cultivation in the Ananthapuramu and Kurnool districts of Andhra Pradesh State. Respondents established a list of climatic, natural, inputs marketing, technical knowhow and policy support constraints and identified high temperatures, availability and access to irrigation water, price and quality of seeds and costs of inputs as the main potential limiting factors of potato yield. A profitability analysis of potato cultivation under different price and yield scenarios, comparing different crops cultivated by the respondents, indicated that potato was an attractive crop in both districts. A sensitivity analysis, however, revealed a low profitability resilience under the unexpectedly worse productivity conditions in the Kurnool district, where the estimated yield level is already significantly lower than in the Ananthapuramu district due to heat stress. The study consequently recommends introduction of potato in the Ananthapuramu district along with a suggested action plan to address the main production constraints and ensure profitability to the farmers.

Profiling of Indian potato cultivars for major 5 nucleotides

A field experiment was carried out during kharif, 2012 at Student’s Farm, College of Agriculture, Rajendranagar, Hyderabad wherein the efficacy of seven insecticides viz., emamectin benzoate 5 SG at 11 g a.i.ha, emamectin benzoate 5 SG at 22 g a.i.ha, profenophos 50 EC at 500 g a.i.ha, profenophos 50 EC at 1000 g a.i.ha, spinosad 45 SC at 100 g a.i.ha, bifenthrin 10 EC at 100 g a.i.ha and Bacillus thuringiensis at 5 WP at 25 g a.i.ha were evaluated against Plutella xylostella on cabbage. The dissipation pattern of profenophos 50 EC (1000 g a.i.ha) and bifenthrin 10 EC (100 g a.i.ha) was studied collecting samples at regular intervals i.e. 0, 1, 3, 5, 7, 10, 15 and 20 days after last spray and analyzed at AINP on Pesticide Residues, Rajendranagar, Hyderabad to know the dynamics of degradation. Another set of cabbage samples collected at regular intervals i.e. 0, 5, 10, 15 and 20 days after last spray and analyzed for profenophos and bifenthrin residues after removing top three layers to know the effect of pre harvest risk mitigation method and removal of profenophos and bifenthrin residues by using validated QuEChERS method. Among all the insecticides, profenophos (1000 g a.i.ha) was found to be the most effective one with a maximum reduction in Plutella xylostella population (70.20%), followed by bifenthrin 10 EC at 100 g a.i.ha (68.18%). The initial deposits of 0.99 mg kg profenophos recorded at 2 hours after last spray dissipated to 0.85, 0.82, 0.16 and 0.07 mg kg by 1, 3, 5 and 7 days after last spray, respectively and below determination level (BDL) by 10 day. Based on the dissipation pattern, a safe waiting period of 15 days was recommended taking into consideration of profenophos MRL (0.01 mg kg) given by EU. The initial deposits of 2.24 mg kg bifenthrin recorded at 2 hours after last spray dissipated to 1.72, 1.38, 0.82 and 0.23 mg kg by 1, 3, 5 and 7 days after last spray, respectively and below determination level (BDL) by10 day. Based on the dissipation pattern a safe waiting period of 2 days was recommended taking into consideration of MRL (1.0 mg kg) given by EU and 3 days was recommended based on the MRL (0.4 mg kg) of CAC. The data collected on removal of profenophos and bifenthrin residues in cabbage by removing top three leaves indicate that 91.91 % of profenophos residues and 25.90 % of bifenthrin residues can be eliminated easily.An experiment comprising levels of liming (liming and no liming), potassium application (0, 500 and 1000 g/tree) and shoot age was conducted in the research farm of Indian Institute of Natural Resins and Gums, Ranchi during 2011-12 to 2013-14 replicated five times to study the effect of soil fertility on rangeeni lac yield in the summer season on medium sized trees. Findings of the experiment indicated that lac yield ratio obtained in liming was 71 percent higher compared to no liming in case of 6 months age of shoots. However, analysis of data revealed that liming has got least effect on older shoots. Its effect was also reflected on yield attribute like sticklac yield. Increased soil fertility due to liming might have supplied better nutrition to the host and the host in turn could supply better nutrition to the insect. Lac yield increased significantly (4 to 7 times) if cultivation is done in older shoots. Interaction effect of liming and potassium was found to be significant in case of 6 months old shoots. Effect of potassium application was observed in the absence of liming and the highest dose could increase lac yield 2.8 times than that of control on six months old shoots. Similarly, liming in the absence of potassium application proved to be the best treatment. Applied potassium might have facilitated host to support nutrition of lac insect in a better way which ultimately increased lac yield.Regeneration competence of pseudobulb segments of Coelogyne ovalis, procured from in vitro grown cultures, was assessed in Mitra medium alone and in combinations with PGRs. Juvenility of the tissues, chemical stimulus, and position of the explants (apical/basal) were the key factors in initiating the response. The explants from pseudobulbs (>3cm long) did not regenerate whereas those from younger(<3cm in length) regenerated depending upon their position in the source organ..The response frequency and time taken for the development of plantlets also varied with the growth stimulus. Maximum number of shoots was obtained from the basal segments on medium supplemented with cytokinin to auxin in ratio of 10:5 in BM+BAP(10 mg l+NAA(5 mgl) , 40 plantlets are formed after 14 wks..The apical segments formed shoots only from apical meristem. The shoots rooted in the same nutrient medium and formed .The regenerated plantlets were acclimatized & transfered to pots filled with moss, pinebark, brick and charcoal pieces mixture with 90% survival.