The red flour beetle, Tribolium castaneum, is a pest of stored products. It is also regarded as a model species for studying development, genetics, biology, physiology and biochemistry. Recently, it has become a model for use in RNA interference experiments. 20-hydroxyecdysone (20E) is involved in insect metamorphosis and its role in organ development in T. castaneum are based on hormonal treatment in conjunction with RNAi. However, information on the biological, morphological and physiological effects of 20E on T. castaneum is still limited. This study reveals the responses of T. castaneum larvae to injections with various doses of 20E (100, 200, 300, 400 and 500 ng / insect). The results show that larvae injected with 20E reached the prepupal, pupal and adult stages earlier than the control group. Different degrees of morphological change were observed in nine traits, including the appearance of pupal prothetelic organs in the larvae. Moreover, an injection of a high dose of 20E reduced the body weights of the resulting insects at each stage, as well as the length and width of elytra. The enzymatic activity of α-amylase in the resulting adults also decreased significantly. This indicates that injection of 20E caused precocious metamorphosis in T. castaneum by inducing changes in morphology and α-amylase activity, and the optimal concentrations that induce such phenomena were in the range of 100-200 ng / insect. Further investigations are needed to examine the roles of 20E in the regulation of α-amylase in T. castaneum., Nujira Tatun, Phiraya Kumdi, Jatuporn Tungjitwitayakul, Sho Sakurai., and Obsahuje bibliografii
Effects of root treatment with 5-aminolevulinic acid (ALA) on leaf photosynthesis in strawberry (Fragaria ananassa Duch.) plants were investigated by rapid chlorophyll fluorescence and modulated 820 nm reflection using 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) and methyl viologen (MV). Our results showed that ALA treatments increased the net photosynthetic rate and decreased the intercelluar CO2 concentration in strawberry leaves. Under DCMU treatment, trapping energy for QA reduction per PSII reaction center increased greatly, indicating DCMU inhibited electron transfer from QA−. The maximum photochemical efficiency of PSII (Fv/Fm) decreased under the DCMU treatment, while a higher Fv/Fm remained in the ALA-pretreated plants. Not only the parameters related to a photochemical phase, but also that one related to a heat phase remained lower after the ALA pretreatment, compared to the sole DCMU treatment. The MV treatment decreased PSI photochemical capacity. The results of modulated 820 nm reflection analysis showed that DCMU and MV treatments had low
re-reduction of P700 and plastocyanin (PSI). However, the strawberry leaf discs pretreated with ALA exhibited high re-reduction of PSI under DCMU and MV treatments. The results of this study suggest that the improvement of photosynthesis by ALA in strawberry was not only related to PSII, but also to PSI and electron transfer chain., Y. P. Sun, J. Liu, R. X. Cao, Y. J. Huang, A. M. Hall, C. B. Guo, L. J. Wang., and Obsahuje bibliografii
The effects of serosally added 5-hydroxytryptamine (5-HT, 100 μM) on the short circuit-current (Isc) across jejunum and ileum taken from fed, starved and undernourished (Gerbillus cheesmani) were investigated. The effects of the neurotoxin, tetrodotoxin (TTX, 10 μM) on the basal Isc as well as on the maximum increase in Isc induced by 5-HT were also studied. There were regional variations in the basal Isc as well as in the way by which the small intestine responds to 5-HT. The basal Isc was greater in jejunum than in ileum and such differences were TTX-sensitive. The maximum increase in Isc, which results from addition of 5-HT, was higher in jejunum than in ileum under all three feeding conditions. TTX reduced the maximum increase in Isc induced by 5-HT across stripped and intact intestine of the two regions in the three nutritional states. The 5-HT-induced Isc in the jejunum of both starved and undernourished gerbils and in the ileum of starved animals was the function of both submucosal and myenteric plexus. In jejunum and ileum taken from starved and undernourished gerbils the 5-HT-induced Isc was both chloride- and bicarbonate-dependent. Thus the results indicated that both starvation and undernourishment increase that response and such increases were TTX-sensitive and both chloride- and bicarbonate-dependent., F. Y. Al-Balool., and Obsahuje bibliografii a bibliografické odkazy
Photosynthetic electron flux allocation, stomatal conductance, and the activities of key enzymes involved in photosynthesis were investigated in Rumex K-1 leaves to better understand the role of nitric oxide (NO) in photoprotection under osmotic stress caused by polyethylene glycol. Gas exchange and chlorophyll fluorescence were measured simultaneously with a portable photosynthesis system integrated with a pulse modulated fluorometer to calculate allocation of photosynthetic electron fluxes. Osmotic stress decreased stomatal conductance, photosynthetic carbon assimilation, and nitrate assimilation, increased Mehler reaction, and resulted in photoinhibition. Addition of external NO enhanced the stomatal conductance, photosynthetic rate, activities of glutamine synthetase and nitrate reductase, and reduced Mehler reaction and photoinhibition. These results demonstrated that osmotic stress reduced CO2 assimilation, decreasing the use of excited energy via CO2 assimilation which caused significant photoinhibition. Improving stomatal conductance by the addition of external NO enhanced the use of excited energy via CO2 assimilation. As a result, less excited energy was allocated to Mehler reaction, which reduced production of reactive oxygen species via this pathway. We suppose that Mehler reaction is not promoted unless photosynthesis and nitrogen metabolism are prominently inhibited. and H. D. Li ... [et al.].
Adenosine is secreted from adipocytes, binds to adenosine A1 receptor and modulates various functions of these cells. In the present study, the effects of an adenosine A1 receptor antagonist (DPCPX; 0.01, 0.1 and 1 μM) on lipogenesis, glucose transport, lipolysis and the antilipolytic action of insulin were tested in rat adipocytes. DPCPX had a very weak effect on lipogenesis and did not significantly affect glucose uptake. In adipocytes incubated with 1 μM DPCPX, lipolysis increased. This effect was blunted by insulin and by a direct inhibitor of protein kinase A. Moreover, 0.1 μM DPCPX substantially enhanced the lipolytic response to epinephrine and increased cAMP in adipocytes. However, DPCPX was ineffective when lipolysis was stimulated by direct activation of protein kinase A. Adipocyte exposure to epinephrine and insulin with or without 0.1 μM DPCPX demonstrated that this antagonist increased the release of glycerol. However, despite the presence of DPCPX, insulin was able to reduce lipolysis. It is concluded that DPCPX had a weak effect on lipogenesis, whereas lipolysis was significantly affected. The partial antagonism of adenosine A1 receptor increased lipolysis in cells incubated with epinephrine alone and epinephrine with insulin due to the synergistic action of 0.1 μM DPCPX and epinephrine., T. Szkudelski, K. Szkudelska, L. Nogowski., and Obsahuje seznam literatury
Arbuscular mycorrhizal fungi (AMF) form symbioses with many plants. Black locust (Robinia pseudoacacia L.) is an important energy tree species that can associate with AMF. We investigated the effects of AMF (Rhizophagus irregularis and Glomus versiforme) on the growth, gas exchange, chlorophyll (Chl) fluorescence, carbon content, and calorific value of black locust seedlings in the greenhouse. The total biomass of the arbuscular mycorrhizal (AM) seedlings was 4 times greater than that of the nonmycorrhizal (NM) seedlings. AMF greatly promoted the photosynthesis of black locust seedlings. AM seedlings had a significantly greater leaf area, higher carboxylation efficiency, Chl content, and net photosynthetic rate (PN) than NM seedlings. AMF also significantly increased the effective photochemical efficiency of PSII and significantly enhanced the carbon content and calorific value of black locust seedlings. Seedlings inoculated with G. versiforme had the largest leaf area and highest biomass, Chl content, PN, and calorific value., X. Q. Zhu, C. Y. Wang, H. Chen, M. Tang., and Obsahuje bibliografii
Brassinosteroids (BRs) have been reported to counteract various stresses. We investigated effects of exogenously applied brassinosteroid, 24-epibrassinolide (EBR), and brassinosteroid-mimic compound, 7,8-dihydro-8α-20-hydroxyecdysone (DHECD), on the photosynthetic efficiency and yield of rice (Oryza sativa L. cv. Pathum Thani 1) under heat stress. Solutions (1 nM) of EBR and DHECD were separately sprayed onto foliage of individual rice plants during their reproductive stage. Five days after the application, the plants were transferred to the day/night temperature regime of 40/30°C for 7 days and then allowed to recover at normal temperature for 7 days. We demonstrated that both DHECD and EBR helped maintain the net photosynthetic rate. The DHECD and EBR application enhanced stomatal conductance, stomatal limitation, and water-use efficiency under the high-temperature regime. DHECD- and EBR-treated plants showed an increase in the nonphotochemical quenching that was lower than that in the control plants. Moreover, DHECD and EBR treatments maintained the maximal quantum efficiency of PSII photochemistry and the efficiency of excitation capture of the open PSII center. Furthermore, the treatments with DHECD or EBR resulted in higher chlorophyll content during the heat treatment compared with the control plants. The paddy field application of 1 nM EBR and/or 1 nM DHECD at the reproductive stage during the hot season could increase the rice yield, especially, the number of filled seeds. DHECD and EBR enhanced total soluble sugar and reducing sugar in straw and more starch was accumulated in rice seeds. Consequently, our results confirmed that DHECD showed biological activities mimicking EBR in the improvement of photosynthetic efficiency and in rising the rice yield under heat stress., J. Thussagunpanit, K. Jutamanee, W. Sonjaroon, L. Kaveeta,
W. Chai-Arree, P. Pankean, A. Suksamrarn., and Obsahuje bibliografii
Ca2+ is an important factor mediating many biotic and abiotic stress responses in plants. In this study, we measured the chlorophyll (Chl) fluorescence of transgenic rice with increased or decreased expression of a calcium-sensing receptor (OsCaS) gene during water deficit caused by polyethylene glycol to prove our hypothesis that increased Ca2+ in combination with increased OsCaS could enhance the drought resistance of transgenic rice. Transcript abundance (evaluated by RT-PCR) was significantly lower in OsCaS antisense line 766 (AS766) than that in the wild type, while the overexpression line 777 (O777) showed four times higher amount than that in the wild type. Chl fluorescence showed that the photochemical quantum yield of PSII in the light increased due to addition of Ca2+ in the O777, but dropped in the AS766. Nonphotochemical quenching increased under stress in both transgenic lines and in the wild type, but less in the O777. Nonregulatory quantum yield of energy dissipation showed no significant change under drought stress. Photochemical quenching was significantly higher in the O777 than those in the AS766 and in the wild type after the Ca2+ treatment. In the absence of stress, the electron transport rate (ETR) was significantly higher in the O777 than in both the AS766 and the wild type. In contrast, the ETR of the wild type and both transgenic lines decreased under drought stress, while the effect of polyethylene glycol was partially alleviated by Ca2+ addition in the O777. In summary, excitation energy conversion and dissipation by PSII were regulated by Ca2+ in the O777. It might partially alleviate the effect of drought stress, whereas addition of Ca2+ had no effect in the wild type and the AS766., R. Wei, Y. Liu, Y. Sui, M. Xu, S. Liu, X. Zhao., and Obsahuje seznam literatury
Heavy metals such as cadmium (Cd) may affect different physiological functions in plants. We carried out a hydroponic experiment under greenhouse conditions in order to evaluate the effect of Cd on photosynthetic and physiological parameters of safflower. The responses of six safflower genotypes (Nebraska-10, 2811, Kouseh, S149, C111, and K12) to four concentrations of CdCl2 (0, 1.5, 3, and 4.5 mg L-1) were examined. Mean shoot and root dry masses of safflower plants were reduced by nearly 57% after the treatment by 4.5 mg(CdCl2) L-1. Contrary to the mean proline content, which increased by 121%, the mean total leaf area per plant, net photosynthetic rate, stomatal conductance to the CO2, leaf chlorophyll a, b, and (a+b), carotenoid content, and quantum efficiency of PSII decreased by 84.4, 50.5, 50.0, 31.6, 32.2, 31.8, 32.9, and 11.2%, respectively, at the presence of 4.5 mg(CdCl2) L-1. The mean Cd concentration in shoots and roots of safflower genotypes exhibited 52- and 157-fold increase, respectively, due to the addition of 4.5 mg(CdCl2) L-1 to the growing media. The mean malondialdehyde content was enhanced by 110% with the increasing CdCl2 concentration, indicating the occurrence of a considerable lipid peroxidation in the plant tissues. Even though the membrane stability index was adversely affected by the application of 1.5 mg(CdCl2) L-1, the decrease ranged from 45 to 62% when plants were treated with 4.5 mg(CdCl2) L-1. Genotype Nebraska-10 seemed to be different from the remaining genotypes in response to the 4.5 mg(CdCl2) L-1; its net photosynthetic rate tended to be the greatest and the Cd concentration in shoots and roots was the lowest among genotypes studied. This study proved Cd-induced decline in growth, photosynthesis, and physiological functions of safflower., L. Moradi, P. Ehsanzadeh., and Obsahuje seznam literatury
Two greenhouse experiments were conducted in order to investigate the effects of different levels of water stress on gas exchange, chlorophyll fluorescence, chlorophyll content, antioxidant enzyme activities, lipid peroxidation, and yield of tomato plants (Solanum lycopersicum cv. Jinfen 2). Four levels of soil water content were used: control (75 to 80% of field water capacity), mild water stress (55 to 60%), moderate water stress (45 to 50%), and severe water stress (35 to 40%). The controlled irrigation was initiated from the third leaf stage until maturity. The results of
two-year trials indicated that the stomatal conductance, net photosynthetic rate, light-saturated photosynthetic rate, and saturation radiation decreased generally under all levels of water stress during all developmental stages, while compensation radiation and dark respiration rate increased generally. Water stress also declined maximum quantum yield of PSII photochemistry, electron transfer rate, and effective quantum yield of PSII photochemistry, while nonphotochemical quenching increased in all developmental stages. All levels of water stress also caused a marked reduction of chlorophyll a, chlorophyll b, and total chlorophyll content in all developmental stages, while activities of antioxidant enzymes, such as superoxide dismutase, peroxidase, and catalase, and lipid peroxidation increased., X. K. Yuan, Z. Q. Yang , Y. X. Li, Q. Liu, W. Han., and Obsahuje seznam literatury