Seed Storage Reserves and Glucosinolates in Brassica rapa L. Grown on the International Space Station

Abstract

<jats:p>Although plants are envisioned to play a central role in life support systems for future long-duration space travel, plant growth in space has been problematic due to horticultural problems of nutrient delivery and gas resupply posed by the weightless environment. Iterative improvement in hardware designed for growth of plants on orbital platforms now provides confidence that plants can perform well in microgravity, enabling investigation of their nutritional characteristics. Plants of <jats:italic>B. rapa</jats:italic> (cv. Astroplants) were grown in the Biomass Production System on the International Space Station. Flowers were hand-pollinated and seeds were produced prior to harvest at 39 days after planting. The material was frozen or fixed while on orbit and subsequently analyzed in our laboratories. Gross measures of growth, leaf chlorophyll, starch and soluble carbohydrates confirmed comparable performance by the plants in spaceflight and ground control treatments. Analysis of glucosinolate production in the plant stems indicated that 3-butenylglucosinolate concentration was on average 75% greater in flight samples than in ground control samples. Similarly, the biochemical make-up of immature seeds produced during spaceflight and fixed or frozen while in orbit was significantly different from the ground controls. The immature seeds from the spaceflight treatment had higher concentrations of chlorophyll, starch, and soluble carbohydrates than the ground controls. Seed protein was significantly lower in the spaceflight material. Microscopy of immature seeds fixed in flight showed embryos to be at a range of developmental stages, while the ground control embryos had all reached the premature stage of development. Storage reserve deposition was more advanced in the ground control seeds. The spaceflight environment thus influences <jats:italic>B. rapa</jats:italic> metabolite production in ways that may affect flavor and nutritional quality of potential space produce.</jats:p>

Gravity control of growth form in Brassica rapa and Arabidopsis thaliana (Brassicaceae): Consequences for secondary metabolism

“…Observations linking hypergravity exposure to an increase in lignin content resulted from exposure to much higher g -forces than those used in this study (e.g., 300g in Tamaoki et al, 2006 and135g in Hoson et al, 1996 ), and were made after incubation at 1g following a short hyperg exposure. Regardless, the decrease in 3-butenyl glucosinolate in response to increasing hypergravity supports previous work, in which glucosinolates in B. rapa plants grown in the microgravity conditions of the ISS increased compared to ground control plants ( Musgrave et al, 2005 ). 8 ).…”

“…In previous studies, we also found that glucosinolates, secondary metabolites that contribute to distinctive fl avors and aromas of cruciferous plants, increased signifi cantly in stems of B. rapa grown in the microgravity conditions of the International Space Station (ISS) compared with the control plants ( Musgrave et al, 2005 ). In the current study, we examined this same class of compounds in hypergravity-grown plants, and in so doing, we tested the hypothesis that hypergravity increases the accumulation of cell wall polymers that are involved in plant structural support, which, in turn, leads to a decrease in nonstructural secondary metabolites in general.…”

Plant cell gravisensitivity and adaptation to microgravity

“…Storage nutrients in Brassicaceae are proteins and lipids (Musgrave et al . ). A later experiment with the same objective on board the ISS confirmed previous data: spaceflight immature embryos had 24% less protein and 117% more starch than those of ground controls (Musgrave et al .…”

“…A later experiment with the same objective on board the ISS confirmed previous data: spaceflight immature embryos had 24% less protein and 117% more starch than those of ground controls (Musgrave et al . ). One reason for such changes in storage accumulation in microgravity could be differences in the closed gaseous microenvironment around the developing seeds.…”

“…In pea seedlings, clinorotation was established to influence gene expression and synthesis of heat shock small molecular proteins (sHsp), especially mitochondrial classes, according to RT‐PCR and Western blot results (Talalaev ; Talalaiev ). During pea seed germination and seedling growth under clinorotation, sHsp cytosolic classes showed retardation of their mRNA degradation.…”