Compensatory abilities depending on seasonal timing of thallus excision of the kelp Undaria pinnatifida cultivated in Matsushima Bay, northern Japan

Improved cultivation technology for the kelp Undaria pinnatifida is greatly needed to increase production to meet increasing commercial demand. A previous cultivation trial indicated that the crop yield of U. pinnatifida sporophytes could be increased greatly by thallus excision in late February due to compensatory growth of the remaining tissues. To develop this potential new cultivation technology, it is essential to identify the time period during which this kelp can compensate and its physiological responses to thallus excision. In this study, U. pinnatifida sporophytes were excised at about 30 cm above the meristem at the beginning of January, February, March, and April, respectively. Morphological features, photosynthesis, nutrient uptake, and carbon and nitrogen contents of excised kelps were measured and compared with these parameters in control kelps grown without excision. Both experimental and control kelps were farmed together in Matsushima Bay, northern Japan. The kelps excised in January and February showed significant increases in the lengths and dry weights of the blade, photosynthetic rates, nutrient uptake rates, and carbon and nitrogen contents compared with the control kelps, and the growth phase was prolonged for at least 1 month. No significant increases were found in dry weights and carbon and nitrogen contents of sporophylls until early April, which indicated that the maturation period was delayed. At the end of this experiment, the nitrogen contents of sporophyll tissues formed after excisions were significantly lower than those of tissues formed before excisions. In contrast, the kelps excised in March and April showed no significant increases in morphological and physiological parameters compared with control kelps. These results suggest that U. pinnatifida sporophytes exhibited great compensation when excisions were conducted during the growing phase in January and February but not in March and April when the maturation phase had started. The regulation of resource allocation to growth and maturation after thallus excisions in January and February likely results in prolongation of the growth phase and maturation phase in excised kelps.     

Compensation of the brown alga Undaria pinnatifida (Laminariales; Phaeophyta) after thallus excision under cultivation in Matsushima Bay, northern Japan

In recent years, the crop yield of cultivated Undaria pinnatifida (Harvey) Suringar has not been able to meet commercial demand and so advances in cultivation technology are strongly needed to increase production. Interestingly, cultivation work has shown the yield of U. pinnatifida sporophytes may be increased significantly by thallus excision, which may cause compensatory growth of the remaining tissues. To test this hypothesis and clarify correlative mechanisms, we examined seasonal morphological characteristics, photosynthetic rates, nutrient uptake rates, and carbon and nitrogen contents of U. pinnatifida sporophytes after thallus excision at a point 30 cm from the meristem in late February and compared these parameters with control kelps grown without excision, which were cultivated together in Matsushima Bay, northern Japan. Compared to control kelps, the length and dry weight of blades increased significantly after excision, and the growth phase was prolonged for about 1 month. The photosynthetic rates, nutrient uptake rates, and carbon and nitrogen contents of excised kelps were significantly higher than those of the controls. After vegetative growth stopped, resources accumulating in thalli were translocated significantly to sporophylls for maturation, indicating maturation was not negatively affected by thallus excision. These results indicate U. pinnatifida exhibits a very strong compensatory ability in response to thallus excision and consequently, the yield could be increased due to an increase in harvest frequency.     

Polycomb Repressive Complex 2 and KRYPTONITE regulate pathogen-induced programmed cell death in Arabidopsis

The Polycomb Repressive Complex 2 (PRC2) is well-known for its role in controlling developmental transitions by suppressing the premature expression of key developmental regulators. Previous work revealed that PRC2 also controls the onset of senescence, a form of developmental programmed cell death (PCD) in plants. Whether the induction of PCD in response to stress is similarly suppressed by the PRC2 remained largely unknown. In this study, we explored whether PCD triggered in response to immunity- and disease-promoting pathogen effectors is associated with changes in the distribution of the PRC2-mediated histone H3 lysine 27 trimethylation (H3K27me3) modification in Arabidopsis thaliana. We furthermore tested the distribution of the heterochromatic histone mark H3K9me2, which is established, to a large extent, by the H3K9 methyltransferase KRYPTONITE, and occupies chromatin regions generally not targeted by PRC2. We report that effector-induced PCD caused major changes in the distribution of both repressive epigenetic modifications and that both modifications have a regulatory role and impact on the onset of PCD during pathogen infection. Our work highlights that the transition to pathogen-induced PCD is epigenetically controlled, revealing striking similarities to developmental PCD.

Changes in histone modifications mediated by Polycomb Repressive Complex 2 and KRYPTONITE play a regulatory role in pathogen-induced programmed cell death in Arabidopsis.     

The effects of desiccation and salinity gradients on the PSII photochemical efficiency of an intertidal brown alga,Sargassum fusiforme from Kagoshima,Japan

The responses of photochemical efficiency to desiccation and salinity gradients in an intertidal edible brown macroalga, Sargassum fusiforme (Harvey) Setchell (Sargassaceae, Fucales), were determined using a pulse amplitude modulation (PAM)-chlorophyll fluorometer. The effective quantum yields (ΔF/F_m'; = Φ_PSII) of photosystem II (PSII) dropped to zero after 360-min aerial exposure under low irradiance (20 μmol photons m⁻² s⁻¹) and 120-min exposure under high irradiance (700 μmol photons m⁻² s⁻¹) for this species at 20°C and 50% relative humidity. Under these conditions, ΔF/F_m' failed to recover to initial levels even after 1-day rehydration in seawater. In general, ΔF/F_m' decreased as desiccation reduced the absolute water content (AWC, %). Nevertheless, when AWC was above ca. 20%, ΔF/F_m' was mostly restored to initial levels after 1-day rehydration in seawater, suggesting strong tolerance to dehydration. Furthermore, S. fusiforme appeared to tolerate a broad range of salinity (i.e. 15–50 psu) during six days of culture; however, ΔF/F_m' declined when salinity was <10 and 60 psu. Strong tolerance to dehydration and salinity stress likely provides S. fusiforme an advantage that allows it to flourish in the intertidal habitat.     

Double-stranded RNA-binding protein DRB3 negatively regulates anthocyanin biosynthesis by modulating PAP1 expression in Arabidopsis thaliana

Journal of Plant Research - The model plant Arabidopsis thaliana has five double-stranded RNA-binding proteins (DRB1-DRB5), two of which, DRB1 and DRB4, are well characterized. In contrast, the...     

Pulmonary aspergillosis due toAspergillus terreus combined with staphylococcal pneumonia and hepatic candidiasis

A female patient with systemic lupus erythematosus (SLE) developed pulmonary aspergillosis with staphylococcal pneumonia and hepatic candidiasis.Aspergillus terreus, which is a rare causative organism of pulmonary aspergilosis, was identified from a pulmonary lesion by culture. The aleurioconidium production, a characeristic of the genusAspergillus sect.terrei, was demonstrated on short and irregular hyphal features in tissue sections. This report is the first of a combined case of pulmonary aspergillosis due toA. terreus with infections caused by other microorganisms.