共查询到5条相似文献,搜索用时 15 毫秒
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Background and AimsPlant reproductive traits are widely understood to be responsive to the selective pressures exerted by pollinators, but there is also increasing evidence for an important role for antagonists such as herbivores in shaping these traits. Many dioecious species show leaky sex expression, with males and females occasionally producing flowers of the opposite sex. Here, we asked to what extent leakiness in sex expression in Mercurialis annua (Euphorbiaceae) might also be plastically responsive to simulated herbivory. This is important because enhanced leakiness in dioecious populations could lead to a shift in both the mating system and in the conditions for transitions between combined and separate sexes.MethodsWe examined the effect of simulated herbivory on the sexual expression of males and females of M. annua in two experiments in which different levels of simulated herbivory led to enhanced leakiness in both sexes.Key ResultsWe showed that leaky sex expression in both males and females of the wind-pollinated dioecious herb M. annua is enhanced in response to simulated herbivory, increasing the probability for and the degree of leakiness in both sexes. We also found that leakiness was greater in larger females but not in larger males.ConclusionsWe discuss hypotheses for a possible functional link between herbivory and leaky sex expression, and consider what simulated herbivory-induced leakiness might imply for the evolutionary ecology of plant reproductive systems, especially the breakdown of dioecy and the evolution of hermaphroditism. 相似文献
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E Lahiani M Dufa? V Castric S Le Cadre D Charlesworth F Van Rossum P Touzet 《Heredity》2013,111(2):157-164
Many flowering plant species exhibit a variety of distinct sexual morphs, the two most
common cases being the co-occurrence of females and males (dioecy) or the co-occurrence of
hermaphrodites and females (gynodioecy). In this study, we compared DNA sequence
variability of the three genomes (nuclear, mitochondrial and chloroplastic) of a
gynodioecious species, Silene nutans, with that of a closely related dioecious
species, Silene otites. In the light of theoretical models, we expect cytoplasmic
diversity to differ between the two species due to the selective dynamics that acts on
cytoplasmic genomes in gynodioecious species: under an epidemic scenario, the
gynodioecious species is expected to exhibit lower cytoplasmic diversity than the
dioecious species, while the opposite is expected in the case of balancing selection
maintaining sterility cytoplasms in the gynodioecious species. We found no difference
between the species for nuclear gene diversity, but, for the cytoplasmic loci, the
gynodioecious S. nutans had more haplotypes, and higher nucleotide diversity,
than the dioecious relative, S. otites, even though the latter has a relatively
high rate of mitochondrial synonymous substitutions, and therefore presumably a higher
mutation rate. Therefore, as the mitochondrial mutation rate cannot account for the higher
cytoplasmic diversity found in S. nutans, our findings support the hypothesis
that gynodioecy in S. nutans has been maintained by balancing selection rather
than by epidemic-like dynamics. 相似文献
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Yasmin Silva Rizk Alice Fischer Marillin de Castro Cunha Patrik Oening Rodrigues Maria Carolina Silva Marques Maria de Fátima Cepa Matos M?nica Cristina Toffoli Kadri Carlos Alexandre Carollo Carla Cardozo Pinto de Arruda 《Memórias do Instituto Oswaldo Cruz》2014,109(8):1050-1056
This study is the first phytochemical investigation of Selaginella sellowii
and demonstrates the antileishmanial activity of the hydroethanolic extract
from this plant (SSHE), as well as of the biflavonoids amentoflavone and
robustaflavone, isolated from this species. The effects of these substances were
evaluated on intracellular amastigotes of Leishmania (Leishmania)
amazonensis, an aetiological agent of American cutaneous leishmaniasis.
SSHE was highly active against intracellular amastigotes [the half maximum inhibitory
concentration (IC50) = 20.2 µg/mL]. Fractionation of the extract led to the isolation
of the two bioflavonoids with the highest activity: amentoflavone, which was about
200 times more active (IC50 = 0.1 μg/mL) and less cytotoxic than SSHE (IC50 = 2.2 and
3 μg/mL, respectively on NIH/3T3 and J774.A1 cells), with a high selectivity index
(SI) (22 and 30), robustaflavone, which was also active against L.
amazonensis (IC50 = 2.8 µg/mL), but more cytotoxic, with IC50 = 25.5
µg/mL (SI = 9.1) on NIH/3T3 cells and IC50 = 3.1 µg/mL (SI = 1.1) on J774.A1 cells.
The production of nitric oxide (NO) was lower in cells treated with amentoflavone
(suggesting that NO does not contribute to the leishmanicidal mechanism in this
case), while NO release was higher after treatment with robustaflavone. S.
sellowii may be a potential source of biflavonoids that could provide
promising compounds for the treatment of cutaneous leishmaniasis. 相似文献
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The bloom‐forming cyanobacterium Microcystis aeruginosa (Kütz.) Kütz. 854 was cultured with 1.05 W · m?2 ultraviolet‐B radiation (UVBR) for 3 h every day, and the CO2‐concentrating mechanism (CCM) within this species as well as effects of UVBR on its operation were investigated. Microcystis aeruginosa 854 possessed at least three inorganic carbon transport systems and could utilize external HCO3? and CO2 for its photosynthesis. The maximum photosynthetic rate was approximately the same, but the apparent affinity for dissolved inorganic carbon was significantly decreased from 74.7 μmol · L?1 in the control to 34.7 μmol · L?1 in UVBR‐treated cells. At 150 μmol · L?1 KHCO3 and pH 8.0, Na+‐dependent HCO3? transport contributed 43.4%–40.2% to the photosynthesis in the control and 34.5%–31.9% in UVBR‐treated cells. However, the contribution of Na+‐independent HCO3? transport increased from 8.7% in the control to 18.3% in UVBR‐treated cells. The contribution of CO2‐uptake systems showed little difference: 47.9%–51.0% in the control and 49.8%–47.2% in UVBR‐treated cells. Thus, the rate of total inorganic carbon uptake was only marginally affected, although UVBR had a differential effect on various inorganic carbon transporters. However, the number of carboxysomes in UVBR‐treated cells was significantly decreased compared to that in the control. 相似文献