Early studies on plant polyamine research pointed to their involvement in responses to different environmental stresses. During the last few years, genetic, transcriptomic and metabolomic approaches have unravelled key functions of different polyamines in the regulation of abiotic stress tolerance. Nevertheless, the precise molecular mechanism(s) by which polyamines control plant responses to stress stimuli are largely unknown. Recent studies indicate that polyamine signalling is involved in direct interactions with different metabolic routes and intricate hormonal cross-talks. Here we discuss the integration of polyamines with other metabolic pathways by focusing on molecular mechanisms of their action in abiotic stress tolerance. Recent advances in the cross talk between polyamines and abscisic acid are discussed and integrated with processes of reactive oxygen species (ROS) signalling, generation of nitric oxide, modulation of ion channel activities and Ca2+ homeostasis, amongst others.

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Polyamines: molecules with regulatory functions in plant abiotic stress tolerance

Applications of genome mapping and marker-assisted selection (MAS) in crop improvement are reviewed. The following aspects are considered: a comparison of the choice of markers available for the generation of linkage maps (including amplified fragment length polymorphisms (AFLP); restriction fragment length polymorphisms (RFLP); randomly amplified polymorphic DNA (RAPD) and simple sequence repeats (SSR)); quantitative trait loci (QTL) analysis; use of molecular markers in the exploitation of hybrid vigour; physical genome mapping; map-based cloning and transposon tagging of agriculturally important genes; synteny in cereal genomes; and the use of MAS in breeding for disease and pest resistance.

Genome mapping, molecular markers and marker-assisted selection in crop plants

Principles of Plant Breeding.

Quantitative trait locus (QTL) mapping is a highly effective approach for studying genetically complex forms of plant disease resistance. With QTL mapping, the roles of specific resistance loci can be described, race-specificity of partial resistance genes can be assessed, and interactions between resistance genes, plant development, and the environment can be analyzed. Outstanding examples include: quantitative resistance to the rice blast fungus, late blight of potato, gray leaf spot of maize, bacterial wilt of tomato, and the soybean cyst nematode. These studies provide insights into the number of quantitative resistance loci involved in complex disease resistance, epistatic and environmental interactions, race-specificity of partial resistance loci, interactions between pathogen biology, plant development and biochemistry, and the relationship between qualitative and quantitative loci. QTL mapping also provides a framework for marker-assisted selection of complex disease resistance characters and the positional cloning of partial resistance genes.

Qtl mapping and quantitative disease resistance in plants

http://www.sidthomas.net/pdf/paperpdfs/108.pdf

Bringing medicinal plants into cultivation: opportunities and challenges for biotechnology

Under optimal conditions of growth, senescence, a terminal phase of development, sets in after a certain physiological age. It is a dynamic and closely regulated developmental process which involves an array of changes at both physiological and biochemical levels including gene expression. A large number of biotic and abiotic factors accelerate the process. Convincing evidence suggests the involvement of polyamines (PAs) and ethylene in this process. Although the biosynthetic pathways of both PAs and ethylene are interrelated, S-adenosylmethionine (SAM) being a common precursor, their physiological functions are distinct and at times antagonistic, particularly during leaf and flower senescence and also during fruit ripening. This provides an effective means for regulation of their biosynthesis and also to understand the mechanism by which the balance between the two can be established for manipulating the senescence process. The present article deals with current advances in the knowledge of the interrelationship between ethylene and PAs during senescence which may open up new vistas of investigation for the future.

Role of polyamines and ethylene as modulators of plant senescence.

Pomegranate biology and biotechnology: A review

An F2 population of pea (Pisum sativum L.) consisting of 174 plants was analysed by restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) techniques. Ascochyta pisi race C resistance, plant height, flowering earliness and number of nodes were measured in order to map the genes responsible for their variation. We have constructed a partial linkage map including 3 morphological character genes, 4 disease resistance genes, 56 RFLP loci, 4 microsatellite loci and 2 RAPD loci. Molecular markers linked to each resistance gene were found: Fusarium wilt (6 cM from Fw), powdery mildew (11 cM from er) and pea common Mosaic virus (15 cM from mo). QTLs (quantitative traits loci) for Ascochyta pisi race C resistance were mapped, with most of the variation explained by only three chromosomal regions. The QTL with the largest effect, on chromosome 4, was also mapped using a qualitative, Mendelian approach. Another QTL displayed a transgressive segregation, i.e. the parental line that was susceptible to Ascochyta blight had a resistance allele at this QTL. Analysis of correlations between developmental traits in terms of QTL effects and positions suggested a common genetic control of the number of nodes and earliness, and a loose relationship between these traits and height.

Restriction fragment length polymorphism analysis of loci associated with disease resistance genes and developmental traits in Pisum sativum L.

Jatropha curcas L. (physic nut) has drawn attention in recent years as a source of seed oil that can provide an economically viable substitute for diesel. Very little work on provenance trials and genetic resources of J. curcas L. has been reported so far. Though J. curcas grows widely in India and several collections of the plant are also maintained, pedigree and provenance records are not always available. This article reports our studies on the diversity amongst the accessions of J. curcas L., both amongst already held collections as well as from a few locations in the wild. Two single-primer amplification reaction (SPAR) methods were used for this purpose. The accessions from the North East were most distant from all other accessions in UPGMA analysis. The NBRI, Bhubaneshwar and Lalkuan accessions were more related to each other. The UPGMA tree clearly shows well-separated accession groups: NBRI, Bhubaneshwar, North East, Lalkuan and Outgroup. The study suggests that this relatively recently introduced plant species shows adequate genetic diversity in India and that the SPAR methods are useful for a rapid assessment of the same. The methods provide important tools for analyzing the diversity within the available collections to shortlist the parental lines for adaptability trials and further improvement of Jatropha plants.

Easy assessment of diversity in Jatropha curcas L. plants using two single-primer amplification reaction (SPAR) methods

Piper betle L is one of the important plants in the Asiatic region which ranks second to coffee and tea in terms of daily consumption Though the plant is known for abuse, in recent years several reports have been published on the effects of the plant extract and chemical constituents on different biological activities in vitro and in vivo The leaf extract, fractions and purified compounds are found to play a role in oral hygiene, anti-diabetic, cardiovascular, anti-inflammatory/immunomodulatory, anti-ulcer, hepato-protective and anti-infective, etc Patents were also awarded for some of the biological activities like anti-inflammatory, anti-cancer and immunomodulatory associated with leaf extracts and purified compounds The active compounds isolated from leaf and other parts are hydroxychavicol, hydroxylchavicol acetate, allypyrocatechol, chavibetol, piperbetol, methylpiperbetol, piperol A and piperol B Phenol-rich leaves of P betle show high antioxidant activities A number of biologically active compounds from P betle have potential for use as medicines, neutraceuticals and industrial compounds Since the traditional use of P betle involves chewing, it offers possibilities of use in drug delivery through buccal mucosa bypassing the gastric route

Shirish A. Ranade

Papers

Role of polyamines and ethylene as modulators of plant senescence.

Pomegranate biology and biotechnology: A review

Restriction fragment length polymorphism analysis of loci associated with disease resistance genes and developmental traits in Pisum sativum L.

Easy assessment of diversity in Jatropha curcas L. plants using two single-primer amplification reaction (SPAR) methods

Piper betle Linn. a maligned Pan-asiatic plant with an array of pharmacological activities and prospects for drug discovery