Microgravity effects on leaf morphology, cell structure, carbon metabolism and mRNA expression of dwarf wheat

Abstract

The use of higher plants as the basis for a biological life support system that regenerates the atmosphere, purifies water, and produces food has been proposed for long duration space missions. The objective of these experiments was to determine what effects microgravity (microg) had on chloroplast development, carbohydrate metabolism and gene expression in developing leaves of Triticum aestivum L. cv. USU Apogee. Gravity naive wheat plants were sampled from a series of seven 21-day experiments conducted during Increment IV of the International Space Station. These samples were fixed in either 3% glutaraldehyde or RNAlater or frozen at -25 degrees C for subsequent analysis. In addition, leaf samples were collected from 24- and 14-day-old plants during the mission that were returned to Earth for analysis. Plants grown under identical light, temperature, relative humidity, photoperiod, CO(2), and planting density were used as ground controls. At the morphological level, there was little difference in the development of cells of wheat under microg conditions. Leaves developed in mug have thinner cross-sectional area than the 1g grown plants. Ultrastructurally, the chloroplasts of microg grown plants were more ovoid than those developed at 1g, and the thylakoid membranes had a trend to greater packing density. No differences were observed in the starch, soluble sugar, or lignin content of the leaves grown in microg or 1g conditions. Furthermore, no differences in gene expression were detected leaf samples collected at microg from 24-day-old leaves, suggesting that the spaceflight environment had minimal impact on wheat metabolism.

Expression of small heat shock protein (sHSP) genes in the garden pea (Pisum sativum) under slow horizontal clinorotation

“…8,9 Our results show that slow clinorotation did not significantly affect the expression of sHSP genes belonging to subfamilies that function in different cellular compartments. These results are consistent with other studies that showed that heat shock proteins were not stimulated in thale cress (Arabidopsis thaliana), 17 wheat (Triticum aestívum) 18 and barley (Hordeum vulgare) 19 plants during spaceflight. Based on these studies, it is logical to conclude that simulated microgravity, unlike temperature, does not result in aberrant protein synthesis or folding and, therefore, does not induce changes in sHSP gene expression at the transcriptional level.…”

“…5 Cultured cells respond by overexpressing a set of heat shock proteins, including sHSP genes. 5,[17][18][19] sHSP gene expression under microgravity was also confirmed by studies using simulated microgravity. 8,9 Our results show that slow clinorotation did not significantly affect the expression of sHSP genes belonging to subfamilies that function in different cellular compartments.…”

“…RNA integrity was verified by agarose gel electrophoresis under denaturing conditions and by spectrophotometric assessment of the 260/280 nm ratio. First strand cDNA synthesis was performed using 1 μg of total RNA pre-treated with DNase I (Thermo Scientific, catalog number EN0525) using oligo-(dT) 18 primers and the Maxima H Minus Reverse Transcriptase (Thermo Scientific, catalog number EP0751) according to the manufacturer's instructions. RT-qPCR reactions were performed by using primers specific for pea sHSPs in a Maxima SYBR Green qPCR Master Mix (Thermo Scientific, catalog: K0241).…”

Spaceflight Transcriptomes: Unique Responses to a Novel Environment

“…This potential arises from the confluence of the lifesupport and astrobiology agendas and has kept plant biology firmly within the spaceflight experiment community. Numerous plant experiments have flown in the Space Shuttle and International Space Station payload programs in the last 20 years, and the following citations are only a sampling of this research: Saunders (1968), Bucker (1974), Krikorian et al (1981Krikorian et al ( , 1992, Kordyum et al (1983), Guikema et al (1994), Kuang et al (1996Kuang et al ( , 2000, Levine and Krikorian (1996), Brown et al (1997), Musgrave et al (1997), Porterfield et al (1997), Adamchuk et al (1999), Kiss and Edelmann (1999), Nedukha et al (1999), Sato et al (1999), Gao et al (2000), Levinskikh et al (2000), Levine et al (2001), Kern and Sack (2001), Paul et al (2001Paul et al ( , 2005, Hoson et al (2003), Klymchuk et al (2003), Stutte et al (2006), Salmi and Roux (2008), Johnsson et al (2009), Kiss et al (2009), Ou et al (2009), Visscher et al (2009. Conclusions from plant biology experiments have highlighted biological responses to spaceflight environments and have also illuminated engineering and operational advancements necessary for conducting sound biological experiments in space (reviewed in Halstead and Dutcher, 1987;Dutcher et al, 1994;Ferl et al, 2002;Clement and Slenzka, 2006;…”

Physiological Responses of Synechocystis sp. PCC 6803 under Clinorotation

“…Studies performed in space or in earth-based simulations indicate that organisms undergo changes when subjected to environmental factors. These changes include thylakoid membrane structure, mitochondria (Popova 2003;Stutte et al 2006;Klimchuk 2007;Brykov 2011), gene expression (Visscher et al 2009), primary (Popova et al 1989;Stutte et al 2006) and secondary metabolism (Musgrave et al 2005;Nechitailo et al 2008) and so on. Many biological samples cited in the above research were harvested just once after a period of space flight or simulation on a clinostat.…”