The effect of a microgravity (space) environment on the expression of expansins from the peg and root tissues of Cucumis sativus

Abstract

In young cucumber seedlings, the peg is a polar outgrowth of tissue that functions by snagging the seed coat, thereby freeing the cotyledons. The development of the peg is thought to be gravity-dependent and has become a model system for plant-gravity response. Peg development requires rapid cell expansion, a process thought to be catalyzed by alpha-expansins, and thus was a good system to identify expansins that were regulated by gravity. This study identified 7 new alpha-expansin cDNAs from cucumber seedlings (Cucumis sativus L. cv Burpee Hybrid II) and examined their expression patterns. Two alpha-expansins (CsExp3 and CsExp4) were more highly expressed in the peg and the root. Earlier reports stated that pegs tend not to form in the absence of gravity, so the expression levels were compared in the pegs of seedlings grown in space (STS-95), on a clinostat, and on earth (1 g). Pegs were observed to form at high frequency on clinostat and space-grown seedlings, yet on clinostats there was more than a 4-fold reduction in the expression of CsExp3 in the pegs of seedlings grown on clinostats vs. those grown at 1 g, while the CsExp4 gene appeared to be turned off (below detection limits). There were no detectable differences in expansin gene expression levels for the pegs of seedlings grown in space or in the orbiter environmental simulator (OES) (1 g) at NASA. The microgravity environment did not affect the expression of CsExp3 or CsExp4, and the clinostat did not simulate the microgravity environment well.

Gravitropic moss cells default to spiral growth on the clinostat and in microgravity during spaceflight

“…But in other cases, rotation versus microgravity produce different responses such as in plant development, movement, and gene expression (Brown 1993;Link et al 2001). Another example is that Arabidopsis roots, which grow down when stationary, coil in clockwise spirals when rotated on a clinostat (Simmons et al 1995;Rutherford and Masson 1996), but not apparently in microgravity (Hoson et al 1999;Kiss et al 2000).…”

Genome histories clarify evolution of the expansin superfamily: new insights from the poplar genome and pine ESTs

“…In the case of LeEXPA10 and RaEXPA4, trees cannot resolve if they belong to clade EXPA-II or EXPA-I. SpEXPA2 appears to belong to a lineage not present in the known angiosperm genomes b Species and references: Car: Cicer arietinum (Sanchez et al 2004), Cpl: Craterostigma plantagineum (Jones and McQueen-Mason 2004), Csa: Cucumis sativus (Shcherban et al 1995;Link et al 2001), Fan: Fragaria ananassa (Civello et al 1999;Harrison et al 2001;Rose et al 1997), Fpa: Festuca pratensis (Reidy et al 2001), Ghi: Gossypium hirsutum (Harmer et al 2002), Gma: Glycine max (Crowell 1994;Lee et al 2003), Les: Lycopersicon esculentum (Rose et al 1997;Reinhardt et al 1998;Brummell et al 1999;Catala et al 2000;Chen and Bradford 2000;Vogler et al 2003), Mac: Musa acuminata (Trivedi and Nath 2004), Mal: Melilotus alba (Giordano and Hirsch 2004), Mdo: Malus × domestica (Wakasa et al 2003), Mja: Mirabilis jalapa (Gookin et al 2003), Nta: Nicotiana tabacum (Link and Cosgrove 1998;Pezzotti et al 2002), Pco: Pyrus communis (Hiwasa et al 2003), Phy: Petunia × hybrida (Zenoni et al 2004), Psa: Pisum sativum (Michael 1996), Rac: Rumex acetosa (Vriezen et al 2000), Rpa: Rumex palustris (Vriezen et al 2000;Colmer et al 2004), Sas: Striga asiatica (O'Malley and Lynn 2000), Sni: Sambucus nigra (Belfield et al 2005), Spy: Sagittaria pygmaea (Ookawara et al 2005), Tve: Triphysaria versicolor (Wrobel and Yoder 2001), Zel: Zinnia elegans (Im et al 2000), Zma: Zea mays (Wu et al 2001;L...…”

Spaceflight Induces Specific Alterations in the Proteomes of Arabidopsis

“…The microgravity environment in itself is outside the evolutionary experience of any terrestrial organism, but the absence of gravity also impacts the physical environment inherent to the unique living space of orbital vehicles (Musgrave et al, 1997;Wolff et al, 2013). It is now well established that plants grown in orbital vehicles exhibit significant changes in gene expression as part of the physiological adaptation to the spaceflight environment (Link et al, 2001;Paul et al, 2001Paul et al, , 2005Paul et al, , 2012bPaul et al, , 2013Stutte et al, 2006;Salmi and Roux, 2008;Salmi et al, 2011;Correll et al, 2013;Nasir et al, 2014;Sugimoto et al, 2014).…”