I am broadly interested in application of genetic principles and tools in various model systems.
Current Projects:
1. Olfactory gene and gustatory gene phylogeny of insects - eg. Tephritidae, Cicadellidae
2. microbial biodiversity in mosquitoes and its influence in mosquito development
3. Role of olfactory genes in vector competance
Past Projects:
I -- Management of fruit flies (Diptera: Tephritidae) and stone weevil (Curculionidae: Coleoptera) infesting fruit crops (see below for details).
II - Genetic basis of compensatory responses following mammalian herbivory (see below for details).
III -- Role of invertase isoforms in compensatory responses following mammalian herbivory (see below for details).
I. Management of fruit flies (Diptera: Tephritidae) and stone weevil (Curculionidae: Coleoptera) infesting fruit crops.
Objectives
1) Development of pre- and postharvest fruit fly management practices in mango
2) Development of pre harvest management practices for stone weevil infesting mango.
3) Training researchers in identification of economically important fruit fly species
4) Coordinating with extension agents for monitoring fruit flies across South India
5) Transfer of technology through extension service.
1) Development of pre- and post harvest fruit fly management practices in mango
(http://upload.wikimedia.org/wikipedia/commons/a/a3/Bactrocera_dorsalis.jpg)
Fruit flies (Tephritidae: Diptera) are economically important pests causing up to 90% yield loss in mango. The gravid female lays eggs in ripening fruits. Later the larvae feed on the fruit pulp, eventually leading to fruit drop. If eggs are laid just before harvest, the hatched larvae are still in harvested fruits causing economic loss after harvest. A sound management practice should include both pre and post-harvest management practices.
The pre harvest management practices include
a) regular sanitation (removal of fallen fruits,
b) insecticidal spray, and
c) regular trapping of male fruit flies using parapheromone methyl eugenol.
The post-harvest management practices include hot water treatment of fruits for specific time.
Publications related to pre and post-harvest management practices – 5, 8, 10, 11 and 12
(http://upload.wikimedia.org/wikipedia/commons/a/a3/Bactrocera_dorsalis.jpg
Current Projects:
1. Olfactory gene and gustatory gene phylogeny of insects - eg. Tephritidae, Cicadellidae
2. microbial biodiversity in mosquitoes and its influence in mosquito development
3. Role of olfactory genes in vector competance
Past Projects:
I -- Management of fruit flies (Diptera: Tephritidae) and stone weevil (Curculionidae: Coleoptera) infesting fruit crops (see below for details).
II - Genetic basis of compensatory responses following mammalian herbivory (see below for details).
III -- Role of invertase isoforms in compensatory responses following mammalian herbivory (see below for details).
I. Management of fruit flies (Diptera: Tephritidae) and stone weevil (Curculionidae: Coleoptera) infesting fruit crops.
Objectives
1) Development of pre- and postharvest fruit fly management practices in mango
2) Development of pre harvest management practices for stone weevil infesting mango.
3) Training researchers in identification of economically important fruit fly species
4) Coordinating with extension agents for monitoring fruit flies across South India
5) Transfer of technology through extension service.
1) Development of pre- and post harvest fruit fly management practices in mango
(http://upload.wikimedia.org/wikipedia/commons/a/a3/Bactrocera_dorsalis.jpg)
Fruit flies (Tephritidae: Diptera) are economically important pests causing up to 90% yield loss in mango. The gravid female lays eggs in ripening fruits. Later the larvae feed on the fruit pulp, eventually leading to fruit drop. If eggs are laid just before harvest, the hatched larvae are still in harvested fruits causing economic loss after harvest. A sound management practice should include both pre and post-harvest management practices.
The pre harvest management practices include
a) regular sanitation (removal of fallen fruits,
b) insecticidal spray, and
c) regular trapping of male fruit flies using parapheromone methyl eugenol.
The post-harvest management practices include hot water treatment of fruits for specific time.
Publications related to pre and post-harvest management practices – 5, 8, 10, 11 and 12
(http://upload.wikimedia.org/wikipedia/commons/a/a3/Bactrocera_dorsalis.jpg
2) Development of pre harvest management practices for stone weevil infesting mango
The mango stone or nut weevil (MSW) Sternochetus mangiferae (Fabricius) (Coleoptera: Curculionidae) is a monophagous pest of mango. It has a univoltine life cycle, most of which, in India, is spent as resting adults from May/June to February/March. When mango fruits are developed to ‘‘pea size’’ (ca.0.5–1 cm diameter) the adults become active and begin feeding and mating. Oviposition on mango fruits begins when the fruits are ‘‘lime size’’ (ca.2–4 cm diameter). The adult female makes a shallow, boat shaped depression in the fruit rind, lays a single egg in the depression, and spreads over the egg a transparent liquid secretion possibly obtained as exudates from cuts made by the female in the surrounding epicarp. This liquid dries as a resin, allowing oviposition sites to be seen as dark brownish spots on the rind. The larva hatches after an incubation period of 5-7 days and burrows through the flesh to reach the seed coat, leaving a visible track as a streak of water area leading to the seed. These early symptoms of oviposition sites and burrowing tracks disappear as the fruit develops. Adults emerge by burrowing through the seed, pulp and rind, congregate in small numbers in cracks and crevices of mango stems, branches, leaf litter, clods, etc., and remain inactive until the next flowering season. The loss due to MSW can range from 5-80% (Verghese, 2000).
Pest Management:
A cover spray of Deltamethrin (0.0028%) reduces infestation by 16.5 – 60.5%.
The mango stone or nut weevil (MSW) Sternochetus mangiferae (Fabricius) (Coleoptera: Curculionidae) is a monophagous pest of mango. It has a univoltine life cycle, most of which, in India, is spent as resting adults from May/June to February/March. When mango fruits are developed to ‘‘pea size’’ (ca.0.5–1 cm diameter) the adults become active and begin feeding and mating. Oviposition on mango fruits begins when the fruits are ‘‘lime size’’ (ca.2–4 cm diameter). The adult female makes a shallow, boat shaped depression in the fruit rind, lays a single egg in the depression, and spreads over the egg a transparent liquid secretion possibly obtained as exudates from cuts made by the female in the surrounding epicarp. This liquid dries as a resin, allowing oviposition sites to be seen as dark brownish spots on the rind. The larva hatches after an incubation period of 5-7 days and burrows through the flesh to reach the seed coat, leaving a visible track as a streak of water area leading to the seed. These early symptoms of oviposition sites and burrowing tracks disappear as the fruit develops. Adults emerge by burrowing through the seed, pulp and rind, congregate in small numbers in cracks and crevices of mango stems, branches, leaf litter, clods, etc., and remain inactive until the next flowering season. The loss due to MSW can range from 5-80% (Verghese, 2000).
Pest Management:
A cover spray of Deltamethrin (0.0028%) reduces infestation by 16.5 – 60.5%.
3) Training sessions to researchers on identification of economically important fruit fly species
Tephritid fruit flies that infest economically important fruit crops like mango, guava, etc belong to dorsalis species complex. Training was provided to researchers (research fellows and scientists) on identification of economically important flies in order to develop risk map that was used by mango export agency to identify fruit fly-free regions.
4) Coordination with extension agents to monitor fruit flies across South India
Coordinated with extension agents across South India to help them to identify fruit fly species across Southern part of India and to develop pre harvest management practices for fruit flies and stone weevil.
Publications related to identification of fruit fly species. – 8
Tephritid fruit flies that infest economically important fruit crops like mango, guava, etc belong to dorsalis species complex. Training was provided to researchers (research fellows and scientists) on identification of economically important flies in order to develop risk map that was used by mango export agency to identify fruit fly-free regions.
4) Coordination with extension agents to monitor fruit flies across South India
Coordinated with extension agents across South India to help them to identify fruit fly species across Southern part of India and to develop pre harvest management practices for fruit flies and stone weevil.
Publications related to identification of fruit fly species. – 8
II -- Genetic basis of compensatory responses following mammalian herbivory
That some plants benefit from being eaten is counterintuitive, yet there is now considerable evidence demonstrating enhanced fitness following herbivory (i.e., plants can overcompensate). Although there is evidence that genetic variation for compensation exists, little is known about the genetic mechanisms leading to enhanced growth and reproduction following herbivory. We took advantage of the compensatory variation in Recombinant Inbred Lines of Arabidopsis thaliana, combined with microarray and QTL (Quantitative Trait Loci) analyses to assess the molecular basis of overcompensation. We found three QTL explaining 11.4%, 10.1% and 26.7% of the variation in fitness compensation, respectively, and 109 differentially expressed genes between clipped and unclipped plants of the overcompensating ecotype Columbia. From the QTL/microarray screen we uncovered one gene that plays a significant role in overcompensation; glucose-6-phosphate-1-dehydrogenase (G6PDH1). Knockout studies of T-DNA insertion lines and complementation studies of G6PDH1 verify its role in compensation. G6PDH1 is a key enzyme in the oxidative pentose-phosphate pathway that plays a central role in plant metabolism. We propose that plants capable of overcompensating reprogram their transcriptional activity by up-regulating defensive genes, genes involved in energy metabolism and increasing DNA content (via endoreduplication) with the increase in DNA content feeding back on pathways involved in defense and metabolism through increased gene expression.
Publications related to genetic basis of compensatory responses: 1 and 2.
Presentation at symposiums or international conference: 1,2,3,4,5 and 6.
III. Role of invertase isoforms in compensatory responses following mammalian herbivory.
Summary: Plant compensatory responses is a mutualistic animal-plant interaction, wherein animals, use >90% of aboveground biomass of plants as nutrition to plants benefit with increased fitness through removal of apical dominance. Though compensatory mechanism is an important defense strategy developed by plants, little is known in terms of its underlying molecular mechanism. Our recent study suggested potential role of two metabolism related genes, glucose-6-phosphate-1-dehydrogenase (G6PDH1) and invertase in plant compensatory responses. Invertase hydrolyzes sucrose to glucose and fructose. The glucose is further catalyzed by G6PDH1 for the production of reductant NADPH for biosynthetic process and down metabolic pathways such as shikimate and glycolysis. In the present study, we evaluated the role of invertase gene family that includes three forms of invertase viz., cell wall, neutral and vacuolar. The gene expression results indicate no significant difference between clipped and unclipped plants and no variation among invertase genes in overcompensating and undercompensating ecotypes, columbia and landsberg erecta, respectively. However, analysis of T-DNA knockout lines of vacuolar and neutral invertase genes indicate its potential role in plant growth and development especially in its contribution to plant fitness. We propose that invertase genes are auto regulatory in function essential for plant growth and development, but the gene responsible for plant compensatory response is G6PDH1.
Publications related to invertase isoforms: # 4
That some plants benefit from being eaten is counterintuitive, yet there is now considerable evidence demonstrating enhanced fitness following herbivory (i.e., plants can overcompensate). Although there is evidence that genetic variation for compensation exists, little is known about the genetic mechanisms leading to enhanced growth and reproduction following herbivory. We took advantage of the compensatory variation in Recombinant Inbred Lines of Arabidopsis thaliana, combined with microarray and QTL (Quantitative Trait Loci) analyses to assess the molecular basis of overcompensation. We found three QTL explaining 11.4%, 10.1% and 26.7% of the variation in fitness compensation, respectively, and 109 differentially expressed genes between clipped and unclipped plants of the overcompensating ecotype Columbia. From the QTL/microarray screen we uncovered one gene that plays a significant role in overcompensation; glucose-6-phosphate-1-dehydrogenase (G6PDH1). Knockout studies of T-DNA insertion lines and complementation studies of G6PDH1 verify its role in compensation. G6PDH1 is a key enzyme in the oxidative pentose-phosphate pathway that plays a central role in plant metabolism. We propose that plants capable of overcompensating reprogram their transcriptional activity by up-regulating defensive genes, genes involved in energy metabolism and increasing DNA content (via endoreduplication) with the increase in DNA content feeding back on pathways involved in defense and metabolism through increased gene expression.
Publications related to genetic basis of compensatory responses: 1 and 2.
Presentation at symposiums or international conference: 1,2,3,4,5 and 6.
III. Role of invertase isoforms in compensatory responses following mammalian herbivory.
Summary: Plant compensatory responses is a mutualistic animal-plant interaction, wherein animals, use >90% of aboveground biomass of plants as nutrition to plants benefit with increased fitness through removal of apical dominance. Though compensatory mechanism is an important defense strategy developed by plants, little is known in terms of its underlying molecular mechanism. Our recent study suggested potential role of two metabolism related genes, glucose-6-phosphate-1-dehydrogenase (G6PDH1) and invertase in plant compensatory responses. Invertase hydrolyzes sucrose to glucose and fructose. The glucose is further catalyzed by G6PDH1 for the production of reductant NADPH for biosynthetic process and down metabolic pathways such as shikimate and glycolysis. In the present study, we evaluated the role of invertase gene family that includes three forms of invertase viz., cell wall, neutral and vacuolar. The gene expression results indicate no significant difference between clipped and unclipped plants and no variation among invertase genes in overcompensating and undercompensating ecotypes, columbia and landsberg erecta, respectively. However, analysis of T-DNA knockout lines of vacuolar and neutral invertase genes indicate its potential role in plant growth and development especially in its contribution to plant fitness. We propose that invertase genes are auto regulatory in function essential for plant growth and development, but the gene responsible for plant compensatory response is G6PDH1.
Publications related to invertase isoforms: # 4