Come, D. 1996, Changes in malondialdehyde content and in superoxide dismutase, catalase and glutahione reductase activities in sunflower seeds as related to deterioration during accelerated aging. -Physiol. P!am.97: 104-110, Sunflower (Helianthus annuus L.) seeds progressively lost their ability to germinate at 25°C, the optimal temperature for germination, after accelerated aging was carried out at 45°C (a temperature too high to permit germination) in water or at 76 or 100% relative humidity (RH), The deleterious effects of the high-temperature treatment increased with increasing seed moisture content. Incubation of seeds at 45 °C in water resulted in electrolyte leakage, which indicated a loss of membrane integrity, A relationship between leakage and loss of seed viability could not be assumed, since no increase in electrolyte efflux occurred after aging at 100% RH. Accelerated aging induced accumulation of malondialdehyde, suggesting that seed deterioration was associated with lipid peroxidation. However, there was no direct relationship between lipid peroxidation and deterioration in membrane integrity. Loss of seed viability was also associated with a decrease in superoxide dismutase, catalase and giutathione reductase activities. Finally, the results obtained suggest that sunflower seed deterioration during accelerated aging is closely related to a decrease in the activities of detoxifying enzymes and to lipid peroxidation.

Late-embryogenesis abundant (LEA) proteins are hydrophilic proteins that accumulate to a high level in desiccation-tolerant tissues and are thus prominent in seeds. They are expected to play a protective role during dehydration; however, functional evidence is scarce. We identified a LEA protein of group 3 (PsLEAm) that was localized within the matrix space of pea (Pisum sativum) seed mitochondria. PsLEAm revealed typical LEA features such as high hydrophilicity and repeated motifs, except for the N-terminal transit peptide. Most of the highly charged protein was predicted to fold into amphiphilic a-helixes. PsLEAm was expressed during late seed development and remained in the dry seed and throughout germination. Application of the stress hormone abscisic acid was found to reinduce the expression of PsLEAm transcripts during germination. PsLEAm could not be detected in vegetative tissues; however, its expression could be reinduced in leaves by severe water stress. The recombinant PsLEAm was shown to protect two mitochondrial matrix enzymes, fumarase and rhodanese, during drying in an in vitro assay. The overall results constitute, to our knowledge, the first characterization of a LEA protein in mitochondria and experimental evidence for a beneficial role of a LEA protein with respect to proteins during desiccation.Late-embryogenesis abundant (LEA) proteins are overwhelmingly hydrophilic proteins that accumulate to high levels in the latter stages of seed maturation and disappear following germination (Galau et al., 1986). While almost ubiquitous in the plant kingdom, data mining has revealed the widespread occurrence of LEA proteins in prokaryotes and eucaryotes (GarayArroyo et al., 2000). Historically clustered in five main groups based on primary structure analysis (Dure et al., 1989;Cuming, 1999), the LEA protein classification was recently reexamined using statistically based bioinformatic tools (Wise, 2003).LEA protein expression, which often appears abscisic acid (ABA) dependent, can also occur in vegetative tissues subjected to water deficit associated with drought, salt, or cold stress (for review, see Ingram and Bartels, 1996;Thomashow, 1998;Cuming, 1999). Both the pattern of expression and the structural features of LEA proteins suggest a general protective role in desiccation tolerance (Ingram and Bartels, 1996;Cuming, 1999). This hypothesis was recently supported by the discovery of a LEA protein in an anhydrobiotic nematode (Browne et al., 2002) as well as by the sensitization to desiccation induced by mutational inactivation of LEA genes in the prokaryote Deinococcus radiodurans (Battista et al., 2001). In view of the apparent lack of well-ordered tertiary structure of LEA proteins preventing their use as catalysts, several mechanisms have been proposed to relate their structural features to the protection of cellular structures required by a dehydrated state: water replacement, ion sequestering, macromolecules, and membrane stabilization (Close, 1996(Close, , 1997Cuming, 1999). Experimentally, sev...

Mitochondria are defining components of most eukaryotes. However, higher plant mitochondria differ biochemically, morphologically, and dynamically from those in other eukaryotes. FRIENDLY, a member of the CLUSTERED MITOCHONDRIA superfamily, is conserved among eukaryotes and is required for correct distribution of mitochondria within the cell. We sought to understand how disruption of FRIENDLY function in Arabidopsis (Arabidopsis thaliana) leads to mitochondrial clustering and the effects of this aberrant chondriome on cell and whole-plant physiology. We present evidence for a role of FRIENDLY in mediating intermitochondrial association, which is a necessary prelude to mitochondrial fusion. We demonstrate that disruption of mitochondrial association, motility, and chondriome structure in friendly affects mitochondrial quality control and leads to mitochondrial stress, cell death, and strong growth phenotypes.