Temperature acclimation of photosynthesis in spinach leaves: analyses of photosynthetic components and temperature dependencies of photosynthetic partial reactions

Spinach (Spinacia oleracea) plants were grown under the day/night temperature regime of 15/10 °C (LT) or 30/25 °C (HT). The plants were also transferred from HT to LT when the sample leaves were at particular developmental stages (HL-transfer). With fully mature leaves, the light-saturated photosynthetic rate (A) at the ambient CO₂ concentration (C_a) of 1500 µL L⁻¹ (A₁₅₀₀) and the initial slope of A versus intercellular CO₂ concentration (C_i) at low C_i region (IS) were obtained to assess capacities of RuBP regeneration and carboxylation. Photosynthetic components including Rubisco and cytochrome f (Cyt f) were also determined. The optimum temperatures for A at C_a of 360 µL L⁻¹ (A₃₆₀), A₁₅₀₀ and IS in HT leaves were 27, 36 and 24 °C, whereas those in LT leaves were 18, 30 and 18 °C. The optimum temperatures in HL-transfer leaves approached those of LT leaves with the increase in the duration at LT. The shift in the optimum temperature was greater and quicker for IS than A₁₅₀₀. By the HL-transfer, the maximum values of A₁₅₀₀ and IS also increased. The maximum A₁₅₀₀ and Cyt f content increased more promptly than IS and Rubisco content. Changes in the Cyt f/Rubisco ratio were reflected to those in the A₁₅₀₀/IS ratio. Taken together, photosynthetic acclimation to low temperature in spinach leaves was due not only to the change in the balance of the absolute rates of RuBP regeneration and carboxylation but also to the large change in the optimum temperature of RuBP carboxylation.     

EXPERIMENTAL CONTROL OF FRUIT-BODY FORMATION IN COPRINUS MACRORHIZUS

In order to establish a proper experimental system for studying the physiological and biochemical processes of fruit-body formation in a Basidiomycetes, Coprinus macrorhizus Rea f. microsporus Hongo, various culture conditions, especially light and temperature, were investigated. The use of homogenates of fruit-body primordia, instead of mycelia, as inocula was effective for maintaining cultures capable of active fruit-body formation during many successive cultivations. At least two successive intermittent illuminations every 12 hr during the 3rd and 4th days of incubation were required for the differentiation of pilei. The most effective wave lengths of incident light were found in the region from 440 to 485 mμ. Temperature effects on fruit-body formation were exhibited in two stages of morphogenesis; i.e., in the induction of primordia formation from vegetative hyphae (by 5°-treatment) and in the transition phase from primordia formation to fruit-body development (by 20°-treatment). Based on these observations, three experimental systems for physiological and biochemical studies on the fruit-body formation have been proposed.     

Evidence from molecular markers and population genetic analyses suggests recent invasions of the Western North Pacific region by biotypes B and Q of Bemisia tabaci (Gennadius)

Invasive events by Bemisia tabaci (Gennadius) biotypes in various parts of the world are of continuing interest. The most famous is biotype B that has caused great economic losses globally. In addition, biotype Q has also recently been reported to be a new invasive pest. These two biotypes have been monitored for some time in the Western North Pacific region, but the invasive events and population genetic structures of these two biotypes are still not clear in this region. In this study, the mitochondrial cytochrome oxidase I (COI) gene was used to reconstruct a phylogenetic tree for identifying biotypes B and Q and to study the relationships between invasive events and ornamental plants. Population genetic analyses of mtCOI sequences were also used to study the genetic relationships within and between populations. A combination of a phylogenetic tree and haplotype analysis suggested the recent invasion of biotype Q in this region is related to the international ornamental trade from the Mediterranean region. Low levels of haplotype diversity and nucleotide diversity indicate that the presence of biotypes B and Q in the Western North Pacific region are caused by multiple invasions. Hierarchical analysis of molecular variance supports the hypothesis of multiple invasions. In addition, high sequence identities and low genetic distances within and between populations of the two biotypes revealed that these invasive events occurred recently. The low levels of genetic differentiation revealed by pairwise F (ST) values between populations also suggests the invasions were recent. Therefore, results of this study suggested that biotypes B and Q entered this region through multiple recent invasions. A quarantine of agricultural crops may be necessary to prevent further invasions.     

Gene conversion limits divergence of mammalian TLR1 and TLR6

Background  

Toll-like receptors (TLR) recognize pathogen-associated molecular patterns and are important mediators of the innate immune system. TLR1 and TLR6 are paralogs and located in tandem on the same chromosome in mammals. They form heterodimers with TLR2 and bind lipopeptide components of gram-positive and gram-negative bacterial cell walls. To identify conserved stretches in TLR1 and TLR6, that may be important for their function, we compared their protein sequences in nine mammalian species(Homo sapiens, Pan troglodytes, Macaca mulatta, Mus musculus, Rattus norvegicus; Erinaceus europaeus, Bos Taurus, Sus scrofa and Canis familiaris).     

The considerable adult size variability in wood feeders is optimal

1. The life history of wood feeders was modelled in order to explain the multiseasonality of development and the great variability of adult size in this group. 2. The model was parameterised with experimental bioenergetic and reproductive data for the xylem feeder Aredolpona rubra (Coleoptera: Cerambycidae). 3. The length of the developmental period, which together with food quality directly determines adult size and indirectly determines the number of eggs laid, was optimised. 4. The results show that multi‐seasonal larval development maximises fitness under conditions of low food quality, relatively low predation pressure, and the presence of hostile periods during the year. 5. The variability of the number of seasons needed to complete development within a wood‐feeder population is a consequence of development time optimisation and the unavoidable extension of the egg‐laying period. These insects have an evolutionary dilemma: to eclose late in a given season at smaller size, bringing about low egg production and low offspring value, or to grow bigger to the next season, jeopardising their lives. 6. The results of the model predict wood‐feeder developmental patterns that depend on the tree tissue inhabited.