Effect of simulated microgravity (µG) conditions on a 3-dimensional (3-D) clinostat on outgrowth of the axillary (lateral) bud induced by a removal of shoot apex (decapitation) in pea (Pisum sativum L. cv. Alaska) seedlings was studied. After decapitation, decapitated seedlings were grown under 1 G or simulated µG conditions on a 3-D clinostat. When decapitation was made at 5 mm below the 1^st node in 5-day-old etiolated pea seedlings, an axillary bud started to outgrow at respective cotyledonary node. The application of auxin (indole-3-acetic acid) to the cut surface at the place of removed shoot apex substantially suppressed axillary bud outgrowth, indicating the outgrowth of axillary buds from the cotyledonary nodes is under the control of transported auxin. The outgrowth of the axillary buds was much larger on a 3-D clinostat than that under 1 G conditions. Similar tendency of the stimulation of axillary bud outgrowth in de-etiolated (light-grown) seedlings on a 3-D clinostat was observed. Together with our previous findings that in etiolated pea seedlings polar auxin transport is substantially reduced under true µG conditions in space as well as simulated ones on a 3-D clinostat, these results suggest that gravity-controlled polar auxin transport is involved in the regulation of decapitation-induced axillary bud outgrowth.

Adhesion, germination and hyphae elongation of/from spores of Aspergillus tonophilus on a silica aerogel were observed, to indicate the possibility of mold contamination of the material designed for astrobiology mission using Kibo module in ISS. Spore germination seemed to be encouraged by nose sebum treatment before adhesion. Spore adhesion was observed by electron microscopy, and autofluorescence from mycelia was observed both by conventional microscope and USB-probe type microscope. The use of latter device was indicated to be effective for the monitoring of possible mold contamination of aerogel samples returned to earth in the astrobiology mission.

3-Hydroxy-3-methylglutaryl-CoA reductase (HMGR) catalyzes the rate-limiting step of the mevalonate pathway for biosynthesis of isoprenoids, such as sterols. An Arabidopsis T-DNA insertion mutant for HMGR1 (hmg1) produced roots, hypocotyls, rosette leaves, and inflorescences after germination at on-orbit 1 g in the Resist Tubule space experiment. The processes up to rosette leaf growth were normal in the hmg1 mutant under microgravity conditions; however, bolting of the inflorescence stem was strongly suppressed. The expression of a series of genes involved in sterol biosynthesis, including sterol glycosyltransferases implicated in producing lipid raft component steryl glycosides, and some of the raft-associated genes in the apical region of inflorescences in the α-tubulin 4 mutant (tua4) was suppressed under microgravity conditions. In addition, the fluorescence due to the raft marker remorin (REM1.3) was uniformly distributed along the rim of the cells of Arabidopsis hypocotyls in microgravity, as in the on-orbit control, showing the presence of lipid rafts in the plasma membrane under microgravity conditions. These results suggest that a severe reduction in sterol levels due to the hmg1 mutation, in combination with downregulation of the expression of sterol biosynthesis genes, causes the suppression of bolting in Arabidopsis under microgravity conditions in space and that lipid rafts may be involved in the bolting.

Tuber formation in potato (Solanum tuberosum L.) under hypergravity conditions in a centrifuge and simulated microgravity (μG) conditions on a horizontal clinostat was studied using in vitro culture of single-nodal stem segments prepared from sprouting tuber shoots. Hypergravity conditions at 100 G for 6 days reduced the growth of axillary bud (or stolon) of a single-nodal stem segment; the length, diameter, and fresh weight of the stolon developed under hypergravity conditions were 53%, 66%, and 74% of 1 G control, respectively. Promotion of swelling seen in the shoot under hypergravity conditions was not observed in the stolon. The size of cells and starch grains in the epidermal tissues in the swelling stolon were reduced under hypergravity conditions. On the other hand, the length of the stolon and the size of the tuber developed in the single-nodal stem segment under simulated μG conditions on a horizontal clinostat for 3 weeks were significantly increased as compared with the 1 G control. These results suggest that stolon growth and tuber formation in the single-nodal stem segment are under the control of gravity. Further studies on the molecular mechanism how gravity regulates tuber development and starch synthesis will be required for increasing potato tuber production in space.

Soy glycinin contains a functional inhibitory sequence, DIpYNP, against muscle-atrophy-associated ubiquitin ligase Cbl-b. It inhibited the binding of Cbl-b and IRS-1 (called Cblin-like peptide) and improved denervation-induced muscle atrophy in mice. In the present study, we evaluated the anti-muscle atrophy effect by feeding Kori-tofu to a mouse model of muscle atrophy induced by sciatic nerve transection, because Kori-tofu is a freeze-dried tofu made mainly from soy proteins. In the mice fed with Kori-tofu for one week, no significant inhibition in the reduction of the tibialis anterior (TA), gastrocnemius (GA) or soleus (SOL) muscle due to denervation was observed, compared with those of mice fed a soy protein isolate (SPI) or casein. However, in the TA muscle of the Kori-tofu-fed group, a significant suppression of the increased expression levels of muscle atrophy-related genes, MAFbx/atrogin-1 and MuRF-1, induced by denervation was observed similarly as that of mice fed a SPI. Additionally, the denervation-mediated decrease in the fast-twitch type myosin heavy chain (MyHC) level was suppressed in the TA of the Kori-tofu-fed group. Thus, our results suggest that Kori-tofu could be a useful and perishable functional space food against unloading-mediated muscle atrophy.