Plant and Cell Physiology Advance Access originally published online on December 10, 2008
Plant and Cell Physiology 2009 50(2):243-253; doi:10.1093/pcp/pcn185
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Seed Dehydration and the Establishment of Desiccation Tolerance During Seed Maturation is Altered in the Arabidopsis thaliana Mutant atem6-1
1Department of Genetics & Biochemistry, 100 Jordan Hall, Clemson University, Clemson, SC 29634, USA
2Department of Biological Sciences, 132 Long Hall, Clemson University, Clemson, SC 29634, USA
*Corresponding author: Email, marcotw{at}clemson.edu; Fax, +864-656-0119.
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Abstract |
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The end of orthodox seed development is typified by a developmentally regulated period of dehydration leading to the loss of bulk water from the entire structure. When dehydration occurs, the cytoplasm condenses and intracellular components become more crowded, providing an environment amenable to numerous undesirable interactions that can lead to protein aggregation, denaturation and organelle–cell membrane fusion. Acquisition of desiccation tolerance, or the ability to withstand these very low water potentials and consequent molecular crowding, has been correlated with the accumulation of various protective compounds including proteins and sugars. Among these are the late embryogenesis abundant (LEA) proteins, a diverse class of highly abundant, heat-stable proteins that accumulate late in embryo maturation coincident with the acquisition of desiccation tolerance. Previous work led us to hypothesize that the protein ATEM6, one of the two Arabidopsis thaliana group 1 LEA proteins, is involved in regulating the rate at which water is lost from the maturing embryo; homozygous atem6-1 mutants display premature dehydration of seeds at the distal end of the silique. Here we demonstrate that rehydrated, mature seeds from atem6-1 mutant plants lose more water during subsequent air drying than wild-type seeds, consistent with a role for ATEM6 protein in water binding/loss during embryo maturation. In addition, and possibly as a result of premature dehydration, mutant seeds along the entire length of the silique acquire desiccation tolerance earlier than their wild-type counterparts. We further demonstrate precocious, and perhaps elevated, expression of the other A. thaliana group 1 LEA protein, ATEM1, that may compensate for loss or ATEM6 expression. However, this observation could also be consistent with acceleration of the entire normal maturation program in atem6-1 mutant embryos. Interestingly, ATEM6 protein does not appear to be required in mature seeds for viability or efficient germination.
Keywords: Arabidopsis - Dehydration - Desiccation tolerance - Germination - LEA protein - Seed maturation
Abbreviations: ANOVA, analysis of variance; daf, days after flowering; GFP, green fluorescent protein; HSP, heat shock protein; LEA, late embryogenesis abundant; LSD, least significant difference; MS, Murashige and Skoog; PEG, polyethylene glycol; PVDF, polyvinylidene fluoride
3Present address: USDA-ARS-AFRS, 2217 Wiltshire Rd, Kearneysville WV 25430, USA.
4Present address: Case Western Reserve University School of Law, 11075 East Boulevard, Cleveland, OH 44106, USA.
(Received November 17, 2008; Accepted November 27, 2008)
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