Abstract
Abstract During germination, orthodox seeds lose their ability to tolerate desiccation resembling recalcitrant seeds. This research aimed to investigate the cell changes during the re-induction of the desiccation tolerance (DT) in Sesbania virgata germinated seeds with 1, 3 and 5 mm long radicles. To re-establish DT, germinated seeds were incubated for 72 h in polyethylene glycol (PEG, -2.04 MPa) before dehydration in silica gel (at 10% moisture content) followed by rehydration. Cell viability was assessed through TUNEL test in dry radicles and transmission electron microscopy in both fresh and dry radicles. The positive-TUNEL confirmed the DNA degradation, through the green fluorescence of the cell nuclei from 5 mm radicle length and the ultra structural evaluations detected loss of cellular content integrity in 3 and 5 mm cell radicles that did not survive dehydration to 10%.
Highlights
The integrity of DNA and cell structures during severe water loss in seeds is predicated on the seeds survival and their capacity of resume their growth after rehydration, suggesting that eventual DNA degradation is linked to death in seeds (Osborne and Boubriak, 1997; Faria et al, 2005)
Tolerance mechanisms (Boubriak et al, 1997). This can be done through techniques such as transmission electron microscopy and TUNEL (Terminal deoxynucleotide transferase (TdT)mediated dUTP nick end labeling) test, in which modified nucleotides are incorporated to extremities of DNA fragments by the terminal deoxynucleotide transferase enzyme (El-Maarouf-Bouteau et al, 2011)
It has previously been shown that there was a relationship between the loss of DNA integrity and loss of desiccation tolerance (DT) in 3 and 5-mmlong radicles of Sesbania virgata (Cav.) (Pers.) (Fabaceae) - a shrub useful in land reclamation - when dehydrated to 10% moisture content, and the cytological assessment of the radical meristem provided evidence of the occurrence of cell death in the 3 and 5-mm-long radicles, which did not survive dehydration (Masetto et al, 2015)
Summary
The integrity of DNA and cell structures during severe water loss in seeds is predicated on the seeds survival and their capacity of resume their growth after rehydration, suggesting that eventual DNA degradation is linked to death in seeds (Osborne and Boubriak, 1997; Faria et al, 2005). Assessment of DNA integrity may help to explain DT and sensitivity, since DNA stability during dehydration or the ability of its repairment upon rehydration is an essential component of the tolerance mechanisms (Boubriak et al, 1997). This can be done through techniques such as transmission electron microscopy and TUNEL (Terminal deoxynucleotide transferase (TdT)mediated dUTP nick end labeling) test, in which modified nucleotides (dUTP) are incorporated to extremities of DNA fragments by the terminal deoxynucleotide transferase enzyme (El-Maarouf-Bouteau et al, 2011). The authors indicated that, this study seeks to understand the nature and extent of damage from intracellular dehydration during the re-establishment of DT in S. virgata germinated seeds
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