Floral herbivory at different stages of flower development changes reproduction in <Emphasis Type="Italic">Iris gracilipes</Emphasis> (Iridaceae)

Floral herbivores and pollinators are major determinants of plant reproduction. Because interaction of floral herbivores and pollinators occurs when herbivores attack the flowers in the bud and flower stages and because the compensatory ability of plants is known to differ according to the timing of herbivory, the effects of herbivory may differ according to its timing. In this study, we investigated the effects of floral herbivory at different stages on fruit production and seed/ovule ratio at two sites of large populations of the perennial herb, Iris gracilipes for 2 years. Herbivory at the bud and fruit stages both tended to have negative effects on fruit production, but the former caused more severe damage. On the other hand, herbivory at the flower stage tended not to have negative effects on fruit production because the degree of flower loss was smaller in the flower stage. Although herbivory decreased fruit production, flowers did not compensate for the damage by increasing the seed/ovule ratio because reproduction of I. gracilipes was limited by pollen availability rather than resources. These results indicate that floral herbivory at different stages has different effects on plant reproduction.     

Single amino acid substitution in the V3 domain of CD4 is responsible for OKT4 epitope deficiency

Address correspondence and offprint requests to: H. Nakauchi.     

Role of decoy molecules in neuronal ischemic preconditioning

AimsDecoy receptors bind with TNF related apoptosis inducing ligands (TRAIL) but do not contain the cytoplasmic domains necessary to transduce apoptotic signals. We hypothesized that decoy receptors may confer neuronal protection against lethal ischemia after ischemic preconditioning (IPC).Main methodMixed cortical neurons were exposed to IPC one day prior to TRAIL treatment or lethal ischemia.Key findingsIPC increased decoy receptor but reduced death receptor expression compared to lethal ischemia. IPC-induced increase in decoy receptor expression was reduced by prior treatment with CAPE, a nuclear factor-kappa B inhibitor (NFκB).SignificanceExpression of decoy molecules, dependent on NFκB, may mediate neuronal survival induced by IPC.     

DOES THE TRADE-OFF BETWEEN GROWTH AND REPRODUCTION SELECT FOR FEMALE-BIASED SEXUAL ALLOCATION IN COSEXUAL PLANTS?

We analyzed sexual allocation in cosexual plants while taking the trade-off between growth and reproduction into consideration and showed that this trade-off does not select for female-biased sexual allocation. There are two problems in sexual allocation: optimizing the amount of resources allocated to reproduction in a growing season and equalizing the resources allocated to the male and the female functions. If these two are possible at the same time, equal resource allocation to the male and the female functions is the evolutionarily stable strategy (ESS; given that the fitness gains through the male and the female functions are proportional to the amount of the resources allocated to these functions). Biased sexual allocation only occurs when constraints make it impossible to simultaneously optimize allocation to reproduction and allocation to male and female functions. However, even if female-biased sexual allocation occurs due to the addition of other constraints, the trade-off between growth and reproduction itself is not an important factor that selects for female-biased sexual allocation.     

Natural cytotoxic autoantibody against thymocytes in spontaneously hypertensive rats

A strain of SHR rats, which spontaneously develops hypertension and periarteritis nodosa, had a decreasing number of rosette-forming T cells in their thymuses and a progressive decline in cellular immune functions by aging. They were found to produce natural thymocytotoxic autoantibody (NTA) detected by a complement-dependent cytotoxicity test. This autoantibody occurred from 1 month of age and throughout life; the incidence was more than 60% of SHR rats at any age. Thymocytes from all six rat strains tested showed similarly high sensitivity to NTA but none of the strains tested produced NTA except the SHR strain. Rosette-forming thymocytes of WKA rats, which were separated by Ficoll gradient, showed much higher cytotoxic sensitivity to NTA than did whole thymocytes and nonrosetting thymocytes. The cytotoxicity of NTA was weak or negative for spleen cells, lymph node cells, bone marrow cells, and blood lymphocytes of WKA rats. However, the cytotoxic activity of NTA was completely absorbed with the thymus, spleen, lymph node cells, and brain homogenates and was partially absorbed with bone marrow cells, but not with liver and kidney homogenates. NTA in SHR rats was an IgM-globulin as determined by sensitivity to 2-ME treatment and by Sephadex G-200 column chromatography. These results suggest that NTA is responsible for the selective suppression of T-cell functions in SHR rats.