Subcellular reorganization of mitochondria producing heavy DNA in aging wheat coleoptiles

Abstract

Unusual closed membrane vesicles containing one or more mitochondria were isolated from homogenates of aging wheat coleoptiles. Very similar (or the same) bodies were shown to exist in situ in vacuoles of undividing cells in the apical part of intact senescent coleoptiles. Vesicles isolated from coleoptile homogenate free of nuclei by 10 min centrifugation at 1700U Ug and traditional mitochondria (sedimented at between 4300U Ug and 17 400U Ug) are similar in respiration rate, composition and content of cytochromes and sensitivity to respiration inhibitors. However, vesicles contain about 2-fold more Ca 2+ ions than free mitochondria do. The specific feature of vesicles containing mitochondria in aging coleoptiles is an intensive synthesis of heavy (b b = 1.718 g/cm 3 ) mitochondrial DNA (H-mtDNA). Thus, aging in plants is accompanied by an increased selective H-mtDNA production and change in subcellular organization of mitochondria.z 1999 Federation of European Biochemical Societies.

Enzymatic DNA Methylation Is an Epigenetic Control for Genetic Functions of the Cell

“…These DNA were found in all archegoniate and flowering plants investigated [97]; synthesis of these DNAs is most strong ly pronounced in aging plant organs (for instance, aging coleoptiles in cereals) [96]. Intense replication of these mtDNAs is one of the specific apoptotic features in plants [98,99].…”

Wheat Endonuclease WEN1 Dependent on S-Adenosyl-L-Methionine and Sensitive to DNA Methylation Status

“…It is very possible that this system operates in plant mitochondria replicating mtDNA very actively in vesicles of plant apoptotic cells. 7 On the other hand, we cannot rule out that WEN1 may take part also in the nuclear DNA degradation as one of the executors of apoptosis in plants. …”

“…These vesicles contain mitochondria with actively replicating mitochondrial DNA. 7 Endonuclease activity was extracted from vesicle fraction by 0.35 M NaCl in 0.8 M sucrose. The enzyme M NaCl in 0.8 M sucrose.…”

“…Wheat (Triticum aestivum L. variety Moskovskaya 35) seedlings were grown as described. 7 Coleoptiles of the 7-day-old seedlings were ground in a mortar with pestle at 4�C in a buffer containing 50 mM Tris-HCl, pH 7.5, 0.4 M sucrose and 1 mg/ �C in a buffer containing 50 mM Tris-HCl, pH 7.5, 0.4 M sucrose and 1 mg/ in a buffer containing 50 mM Tris-HCl, pH 7.5, 0.4 M sucrose and 1 mg/ ml bovine serum albumin (BSA). Homogenate was filtered trough three gauze layers and centrifuged at 600 x g for 15 min.…”

“…Supernatant was centrifuged at 1500 x g for 15 min. The sediment obtained, containing mainly cellular vesicles, 7 was washed with same buffer but without BSA and used for isolation of enzyme.…”