Genome Analysis of Cytochrome P450s and Their Expression Profiles in Insecticide Resistant Mosquitoes, Culex quinquefasciatus

Here we report a study of the 204 P450 genes in the whole genome sequence of larvae and adult Culex quinquefasciatus mosquitoes. The expression profiles of the P450 genes were compared for susceptible (S-Lab) and resistant mosquito populations, two different field populations of mosquitoes (HAmCq and MAmCq), and field parental mosquitoes (HAmCq G0 and MAmCqG0) and their permethrin selected offspring (HAmCq G8 and MAmCqG6). While the majority of the P450 genes were expressed at a similar level between the field parental strains and their permethrin selected offspring, an up- or down-regulation feature in the P450 gene expression was observed following permethrin selection. Compared to their parental strains and the susceptible S-Lab strain, HAmCqG8 and MAmCqG6 were found to up-regulate 11 and 6% of total P450 genes in larvae and 7 and 4% in adults, respectively, while 5 and 11% were down-regulated in larvae and 4 and 2% in adults. Although the majority of these up- and down-regulated P450 genes appeared to be developmentally controlled, a few were either up- or down-regulated in both the larvae and adult stages. Interestingly, a different gene set was found to be up- or down-regulated in the HAmCqG8 and MAmCqG6 mosquito populations in response to insecticide selection. Several genes were identified as being up- or down-regulated in either the larvae or adults for both HAmCqG8 and MAmCqG6; of these, CYP6AA7 and CYP4C52v1 were up-regulated and CYP6BY3 was down-regulated across the life stages and populations of mosquitoes, suggesting a link with the permethrin selection in these mosquitoes. Taken together, the findings from this study indicate that not only are multiple P450 genes involved in insecticide resistance but up- or down-regulation of P450 genes may also be co-responsible for detoxification of insecticides, insecticide selection, and the homeostatic response of mosquitoes to changes in cellular environment

Drought tolerance in two oil palm hybrids as related to adjustments in carbon metabolism and vegetative growth

Drought tolerance was examined in two oil palm hybrids (BRS Manicoré and BRS C 2501) grown in large pots and subjected to long-term drought (57 days) and rehydration. Regardless of hybrids, predawn water potential (Ψ pd), net photosynthesis rates, and stomatal conductance decreased similarly upon drought imposition, but the absolute values of these variables were lower in BRS C 2501 than in BRS Manicoré. Overall, drought-induced decreases in activities of key enzymes associated with carbon metabolism, including Rubisco, ADP-glucose pyrophosphorylase, and sucrose-phosphate synthase, were stronger in BRS C 2501 than in BRS Manicoré. Our data suggest that synthesis of starch (and possibly sucrose) was fundamentally limited by a lower substrate availability rather than by enzymatic constraints, particularly until day 34 after suspending watering. Drought stress provoked similar decreases in biomass accumulation in either hybrid; however, BRS Manicoré plants displayed higher total leaf area and root length coupled with greater relative decreases in dry matter of above-ground parts than of roots as compared to BRS C 2501, thereby leading to an increased root-to-above ground ratio in the former. Upon resuming irrigation, the slow recovery of Ψ pd preceded the recovery of stomatal conductance and photosynthesis irrespective of hybrid. BRS Manicoré was better able to recover enzyme activities and carbohydrate status than BRS C 2501. In conclusion, both hybrids could tolerate (or survive) the severe drought conditions, but, overall, BRS Manicoré plants were better able to adjust its physiological, morphological, and biochemical traits to cope with drought than did BRS C 2501

Drought tolerance in two oil palm hybrids as related to adjustments in carbon metabolism and vegetative growth

Drought tolerance was examined in two oil palm hybrids (BRS Manicoré and BRS C 2501) grown in large pots and subjected to long-term drought (57 days) and rehydration. Regardless of hybrids, predawn water potential (Ψ pd), net photosynthesis rates, and stomatal conductance decreased similarly upon drought imposition, but the absolute values of these variables were lower in BRS C 2501 than in BRS Manicoré. Overall, drought-induced decreases in activities of key enzymes associated with carbon metabolism, including Rubisco, ADP-glucose pyrophosphorylase, and sucrose-phosphate synthase, were stronger in BRS C 2501 than in BRS Manicoré. Our data suggest that synthesis of starch (and possibly sucrose) was fundamentally limited by a lower substrate availability rather than by enzymatic constraints, particularly until day 34 after suspending watering. Drought stress provoked similar decreases in biomass accumulation in either hybrid; however, BRS Manicoré plants displayed higher total leaf area and root length coupled with greater relative decreases in dry matter of above-ground parts than of roots as compared to BRS C 2501, thereby leading to an increased root-to-above ground ratio in the former. Upon resuming irrigation, the slow recovery of Ψ pd preceded the recovery of stomatal conductance and photosynthesis irrespective of hybrid. BRS Manicoré was better able to recover enzyme activities and carbohydrate status than BRS C 2501. In conclusion, both hybrids could tolerate (or survive) the severe drought conditions, but, overall, BRS Manicoré plants were better able to adjust its physiological, morphological, and biochemical traits to cope with drought than did BRS C 2501

Leaf gas exchange and multiple enzymatic and non-enzymatic antioxidant strategies related to drought tolerance in two oil palm hybrids

Drought is a major environmental constraint limiting growth and yield of oil palm trees. In this study, two oil palm hybrids (BRS Manicoré and BRS C 2501) were grown in large containers and subjected to a water deficit during 57 days. Leaf gas exchange analysis was combined with an in-depth assessment of the antioxidant system over the drought imposition. Under drought, leaf water potential at predawn (Ψ pd) decreased similarly in both hybrids. In parallel, there were decreases in the net CO2 assimilation rate (A), chlorophyll concentrations and Rubisco total activity. Overall, these decreases were more pronounced in BRS C 2501 than in BRS Manicoré. BRS C 2501 plants triggered more markedly its enzymatic antioxidant system earlier (Ψ pd = −2.1 MPa) than did BRS Manicoré, but these responses were accompanied by higher concentrations of H2O2 and malondialdehyde in BRS C 2510 than in BRS Manicoré. With the progress of drought stress (Ψ pd = −2.9 MPa and below), BRS Manicoré was better able to cope with oxidative stress through a more robust antioxidant system. In addition, significant decreases in drought-induced NAD+-malate dehydrogenase activities were only observed in stressed BRS C 2501 plants. Regardless of watering regimes, the total carotenoid, ascorbate and glutathione concentrations were higher in BRS Manicoré than in BRS C 2501. In conclusion, BRS Manicoré is better able to tolerate drought than BRS C 2501 by triggering multiple antioxidant strategies involved both in reactive oxygen species scavenging and dissipation of excess energy and/or reducing equivalents particularly under severe drought stress