Vivek Prasad

A systemic antiviral resistance-inducing protein isolated from Clerodendrum inerme Gaertn. is a polynucleotide:adenosine glycosidase (ribosome-inactivating protein)

Two systemic antiviral resistance‐inducing proteins, CIP‐29 and CIP‐34, isolated from Clerodendrum inerme Gaertn. leaves, were tested for ribosome‐inactivating properties. It was found that CIP‐29 has the characteristics of a polynucleotide: adenosine glycosidase (ribosome‐inactivating protein), in that it inhibits protein synthesis both in cell‐free systems and, at higher concentrations, in cells, and releases adenine from ribosomes, RNA, poly(A) and DNA. As compared with other known RIPs, CIP‐29 deadenylates DNA at a high rate, and induces systemic antiviral resistance in susceptible plants.

Two basic proteins isolated from Clerodendrum inerme Gaertn. are inducers of systemic antiviral resistance in susceptible plants

Abstract Several species of higher plants show antiviral activity manifested either as an inactivation of virus in vitro, or as induced resistance. Two basic glycoproteins from leaves of Clerodendrum inerme Gaertn. have been purified and their characteristics compared. Both of these, called CIP-29 and CIP-34, induce an actinomycin-D sensitive systemic resistance against tobacco mosaic virus in Nicotiana tabacum cv. Samsun NN, although the minimum amount of purified protein required to induce the same degree of resistance varies from 16 μg/ml for CIP-29 to 800 μg/ml for CIP-34. CIP-29 and CIP-34 have molecular masses of 29 and 34 kDa, respectively. The two also differ in that CIP-29 is a monomer while CIP-34 is a complex. Both proteins can tolerate high temperatures (up to 80°C) and protease digestion (up to 48 h). Though their properties are similar to those of the ribosome-inactivating proteins possessing antiviral properties, they do not cross-react with antisera raised against dianthin, momordin and saporin, the RIPs isolated from Dianthus caryophyllus, Momordica and Saponaria officinalis .

A PCR-based assessment of genetic diversity, and parentage analysis among commercial mango cultivars and hybrids

Summary Three different PCR methods [Random Amplified Polymorphic DNA (RAPD), Inter-Simple Sequence Repeats (ISSR), and Directed Amplification of Minisatellite DNA (DAMD)] were used to analyse genetic diversity and parentage among 20 mango cultivars, including 18 landraces and two hybrids (‘Amrapali’ and ‘Mallika’). These hybrids together with a third hybrid (‘Ratna’), and an out-group species (Mangifera sylvatica) were also analysed for parentage. Fifteen, seven and four primers were used to amplify a total of 158, 69 and 59 distinct DNA fragments by RAPD, ISSR and DAMD, respectively. Of these, approx. 85%, 64% and 90% were polymorphic, respectively. Genetic distances between pairs of mango cultivars were measured separately by each method and depicted graphically as a Neighbor Joining (NJ) tree. The three methods revealed different groupings of cultivars and hybrids. A NJ tree based on the cumulative data from all methods correlated well with the parentage of the mango hybrids, and the grouping of cultivars on a regional basis. Genetic markers likely to be associated with important agronomic traits were identified by further analysing the hybrids, with their respective parents, using all three methods. On the basis of the highest number of polymorphic bands observed (90%), DAMD was judged to be the best method with which to analyse mango germplasm.

A Functional Genomic Perspective on Drought Signalling and its Crosstalk with Phytohormone-mediated Signalling Pathways in Plants

Introduction: Drought stress is one of the most important abiotic stresses that negatively influence crop performance and productivity. Plants acclimatize to drought stress conditions through altered molecular, biochemical and physiological responses. Gene and/or protein expression and regulation are thought to be modulated upon stress perception and signal transduction for providing requisite endurance to plants. Plant growth regulators or phytohormones are important molecules required for various biological processes in plants and are also central to stress signalling pathways. Among various phytohormones, Abscisic Acid (ABA) and Ethylene (ET) are considered to be the most vital growth regulators implicated in drought stress signalling and tolerance. Besides the above two known classical phytohormones, Salicylic Acid (SA) and Jasmonic Acid (JA) have also been found to potentially enhance abiotic stress tolerance particularly that of drought, salinity, and heat stress tolerance in plants. Apart from these several other growth regulators such as Cytokinins (CKs), Auxin (AUX), Gibberellic Acid (GA), Brassinosteroids (BRs) and Strigolactones (SLs) have also been reported to actively participate in abiotic stress responses and tolerance in plants. The abiotic stress signalling in plants regulated by these hormones further depends upon the nature, intensity, and duration of exposure to various environmental stresses. It has been reported that all these phytohormones are also involved in extensive crosstalk and signal transduction among themselves and/or with other factors. Conclusion: This review thus summarizes the molecular mechanism of drought signalling and its crosstalk with various phytohormone signalling pathways implicated in abiotic stress response and tolerance.

Bacillus amyloliquefaciens Confers Tolerance to Various Abiotic Stresses and Modulates Plant Response to Phytohormones through Osmoprotection and Gene Expression Regulation in Rice

Being sessile in nature, plants have to withstand various adverse environmental stress conditions including both biotic and abiotic stresses. Comparatively, abiotic stresses such as drought, salinity, high temperature, and cold pose major threat to agriculture by negatively impacting plant growth and yield worldwide. Rice is one of the most widely consumed staple cereals across the globe, the production and productivity of which is also severely affected by different abiotic stresses. Therefore, several crop improvement programs are directed toward developing stress tolerant rice cultivars either through marker assisted breeding or transgenic technology. Alternatively, some known rhizospheric competent bacteria are also known to improve plant growth during abiotic stresses. A plant growth promoting rhizobacteria (PGPR), Bacillus amyloliquefaciens NBRI-SN13 (SN13) was previously reported by our lab to confer salt stress tolerance to rice seedlings. However, the present study investigates the role of SN13 in ameliorating various abiotic stresses such as salt, drought, desiccation, heat, cold, and freezing on a popular rice cv. Saryu-52 under hydroponic growth conditions. Apart from this, seedlings were also exogenously supplied with abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA) and ethephon (ET) to study the role of SN13 in phytohormone-induced stress tolerance as well as its role in abiotic and biotic stress cross-talk. All abiotic stresses and phytohormone treatments significantly affected various physiological and biochemical parameters like membrane integrity and osmolyte accumulation. SN13 also positively modulated stress-responsive gene expressions under various abiotic stresses and phytohormone treatments suggesting its multifaceted role in cross-talk among stresses and phytohormones in response to PGPR. To the best of our knowledge, this is the first report on detailed analysis of plant growth promotion and stress alleviation by a PGPR in rice seedlings subjected to various abiotic stresses and phytohormone treatments for 0, 1, 3, 10, and 24 h.

SYSTEMIC ANTIVIRAL RESISTANCE INDUCED IN PAPAYA BY CAP-34, A RESISTANCE INDUCING PROTEIN FROM CLERODENDRUM ACULEATUM, IS ASSOCIATED WITH A PROTEINACEOUS VIRUS INHIBITORY ACTIVITY

Proteins from non-host higher plants are known to induce systemic resistance in plants against virus infections in susceptible plants. CAP-34 is one such known protein with molecular mass 34 kDa, isolated from Clerodendrum aculeatum. CAP-34 was also shown to be acting against Papaya ringspot virus (PRSV) in papaya by imposing a possible check on PRSV replication. Since the induced resistance was systemic, efforts were made to identify host components that could be involved in it. In the process, a virus inhibitory activity was observed concomitantly with the development of resistance. This paper reports the time- course of the virus inhibitory activity and purification to electrophoretic homogeneity of a proteinaceous virus inhibitory agent (VIA), and the determination of some of its biochemical characteristics. This VIA, denoted CP-VIA-34 based on the host where it came from (Carica papaya), and was determined to be a basic protein that inactivated Tobacco mosaic virus (TMV) ex vivo when bioassayed on Nicotiana tabacum cv Samsun NN. CP-VIA-34 had a molecular mass of 34 kDa, was thermostable and resistant to proteinase K. It did not exhibit protease (tested separately on BSA, and purified TMV), DNase and RNase activities. The paper discusses the characteristics of the CP-VIA-34, and its relevance in relation to some other known plant defence proteins such as the ribosome-inactivating proteins, inhibitor of virus replication, antiviral factor, and the PR-proteins.

BDP-30, a systemic resistance inducer from Boerhaavia diffusa L., suppresses TMV infection, and displays homology with ribosome-inactivating proteins

Root extract of Boerhaavia diffusa L. induced systemic resistance in tobacco against Tobacco mosaic virus. A 30 kDa protein was isolated as the active component, called BDP-30 on the basis of the molecular weight and source plant. BDP-30, a glycoprotein, was found to be temperature and protease resistant. It was basic, possessing a pI greater than 9.0. In-gel proteolytic digestion of BDP-30 generated two peptides that possessed the amino acid sequence KLYDIPPLR and KVTLPYSGNYER by LC/MS/MS. Both peptides shared absolute sequence identity with trichosanthin, a ribosome-inactivating protein from Trichosanthes kirilowii, and a 78% and 100% homology respectively with an RIP from Bryonia dioica, bryodin. Further, effort was made to look at the fate of TMV in induced resistant Nicotiana tabacum cv. Xanthi, a systemic host of the virus, at specified days after inoculation in control and treated plants. TMV coat protein (CP) was detected by immunoblot 7 days post inoculation up to 21 days in the control set, but not in treated resistant plants. TMV RNA was detected by RT-PCR using TMV-CP specific primers. Resistant tobacco did not show presence of TMV RNA up to 21 days of inoculation. This suggests that BDP-30 may be suppressing TMV replication.

Purification of Two Basic 1, 3-b-Glucanase Isoforms from Cyamopsis tetragonoloba (L.)Taub. Induced to Resist Virus Infections

1,3-b-glucanases (EC 3.2.1.39) are enzymes that degrade polysaccharidic substratesand have antimicrobial activity against fungi and bacteria. They have also been implicated in systemic acquired resistance (SAR) indirectly through release of endogenous elicitor molecules. SAR against viruses can be induced in plants by a few substances, including proteins isolated from some non-host plants. In the present study, CAP-34, a 34 kDa basic protein isolated from Clerodendrumaculeatum L., was used to induce systemic resistance against sunnhemp rosette virusin Cyamopsis tetragonoloba (L.) Taub. 1,3-b-glucanase activity increased rapidlyfollowing treatment with CAP-34. The glucanase induction started within 3 h oftreatment, and maintained a peak value between 6 and 24 h before declining between48 and 72 h. Two isoforms were purified from resistant C. tetragonoloba. Both were basic and possessed an Mr of 34 and 36 kDa. Their pI was greater than pH 9.3. p Hoptima were 5.5 and 5.6 for the 34 and 36 kDa isoforms, respe...

Chapter 13 – Insect Viruses

Food security has been a concern for many years, and one of the principal causes of loss of food has been preharvest destruction by pathogens and pests. Successful control of these has been possible with the use of chemicals; however, it is now recognized that chemical residues left behind on the crop may be harmful to the consumer. This provided an impetus to search for alternative means of controlling pathogens and pests, especially methods relying on biological agents or their products. Ecosystems are in a state of dynamic equilibrium, and nature itself offers solutions in the form of a set of organisms devouring or damaging others for their own survival. The various biological entities that are used either alone or in combination with others, and the processes by which these are done, collectively fall within integrated pest management (IPM). IPM strategies are now being strongly advocated to combat plant disease and pest attack. Several viruses have been identified that destroy insects, without any adverse effect on humans, and are good candidates for insect control. This chapter summarizes the various virus groups with antiinsect behavior and gives a detailed account of the baculoviruses that have been used most extensively, and commercial products that are also freely available for field use.

Paenibacillus lentimorbus induces autophagy for protecting tomato from Sclerotium rolfsii infection

During biotic stress, plants use several mechanisms to protect themselves that include the production of reactive oxygen species (ROS), induction of pathogenesis-related proteins and cell death. Some plant growth promoting rhizobacteria (PGPR) are known to act as bio-control agents that protect crops against pathogens. The biocontrol activity of PGPR Paenibacillus lentimorbus (B-30488) against Sclerotium rolfsii showed previously where several defense-related genes were upregulated with ROS induction in tomato. We further evaluate the other possibility, i.e. role of autophagy in enhancing defense in tomato using PGPR. Confocal microscopy revealed the presence of an acidotropic dye Mono Dansyl Cadaverine (MDC) stained autophagosomes in B-30488 treated healthy and infected plants. These autophagosomes almost disappeared in plants treated with an autophagy inhibitor chloroquine. The results were also confirmed by ultrastructural analysis of leaf tissues using transmission electron microscopy. Enhanced expression of autophagy-related genes was also monitored in B-30488 primed fungal infected tissues as compared to control by qRT-PCR. Results of ROS accumulation, fluorescence, confocal and transmission electron microscopy and gene expression analysis revealed induction of autophagy using B-30488 as a biocontrol agent suggesting a role in enhancing disease resistance in tomato. Overall, the present study indicated a role of B-30488 as a biocontrol in enhancing disease resistance in tomato and also assists a better understanding of fungal pathogenesis that is expected to be useful in developing new strategies for disease control.