Molecular characterization of SrSTP14, a sugar transporter from thermogenic skunk cabbage, and its possible role in developing pollen.

In floral thermogenesis, sugars play an important role not only as energy providers but also as growth and development facilitators. Yet, the mechanisms underlying sugar translocation and transport in thermogenic plants remain to be studied. Asian skunk cabbage (Symplocarpus renifolius) is a species that can produce durable and intense heat in its reproductive organ, the spadix. Significant morphological and developmental changes in the stamen are well-characterized in this plant. In this study, we focused on the sugar transporters (STPs), SrSTP1 and SrSTP14, whose genes were identified by RNA-seq as the upregulated STPs during thermogenesis. Real-time PCR confirmed that mRNA expression of both STP genes was increased from the pre-thermogenic to the thermogenic stage in the spadix, where it is predominantly expressed in the stamen. SrSTP1 and SrSTP14 complemented the growth defects of a hexose transporter-deficient yeast strain, EBY4000, on media containing 0.02, 0.2, and 2% (w/v) glucose and galactose. Using a recently developed transient expression system in skunk cabbage leaf protoplasts, we revealed that SrSTP1 and SrSTP14-GFP fusion proteins were mainly localized to the plasma membrane. To dig further into the functional analysis of SrSTPs, tissue-specific localization of SrSTPs was investigated by in situ hybridization. Using probes for SrSTP14, mRNA expression was observed in the microspores within the developing anther at the thermogenic female stage. These results indicate that SrSTP1 and SrSTP14 transport hexoses (e.g., glucose and galactose) at the plasma membrane and suggest that SrSTP14 may play a role in pollen development through the uptake of hexoses into pollen precursor cells.

Modeling future wildlife habitat suitability: serious climate change impacts on the potential distribution of the Rock Ptarmigan Lagopus muta japonica in Japan's northern Alps.

BACKGROUND: The Rock Ptarmigan Lagopus muta japonica lives in the alpine zones of central Japan, which is the southern limit of the global distribution for this species. This species is highly dependent on alpine habitats, which are considered vulnerable to rapid climate change. This study aimed to assess the impact of climate change on potential L. muta japonica habitat based on predicted changes to alpine vegetation, to identify population vulnerability under future climatic conditions for conservation planning. We developed species distribution models, which considered the structure of the alpine ecosystem by incorporating spatial hierarchy on specific environmental factors to assess the potential habitats for L. muta japonica under current and future climates. We used 24 general circulation models (GCMs) for 2081-2100 as future climate conditions. RESULTS: The predicted potential habitat for L. muta japonica was similar to the actual distribution of the territories in the study area of Japan's northern Alps (36.25-36.5°N, 137.5-137.7°E). Future potential habitat for L. muta japonica was projected to decrease to 0.4% of the current potential habitat in the median of occurrence probabilities under 24 GCMs, due to a decrease in alpine vegetation communities. Some potential habitats in the central and northwestern part of the study area were predicted to be sustained in the future, depending on the GCMs. CONCLUSIONS: Our model results predicted that the potential habitats for L. muta japonica in Japan's northern Alps, which provides core habitat for this subspecies, would be vulnerable by 2081-2100. Small sustainable habitats may serve as refugia, facilitating the survival of L. muta japonica populations under future climatic conditions. Impact assessment studies of the effect of climate change on L. muta japonica habitats at a nationwide scale are urgently required to establish effective conservation planning for this species, which includes identifying candidate areas for assisted migration as an adaptive strategy.