Cell changes during the re-induction of desiccation tolerance in germinated seeds of Sesbania virgata (Cav.) Pers.

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%.Index terms: cell viability, transmission electron microscopy, TUNEL test.Mudanças celulares durante a re-indução da tolerância à dessecação em sementes germinadas de Sesbania virgata (Cav.) Pers.RESUMO -Durante a germinação, as sementes ortodoxas perdem sua habilidade de tolerar a dessecação assemelhando-se com as sementes recalcitrantes. Este trabalho objetivou investigar as mudanças celulares que ocorrem durante a re-indução da tolerância à dessecação (TD) em sementes germinadas de Sesbania virgata com 1, 3 e 5 mm de comprimento de radícula. Para restabelecer a TD, as sementes germinadas foram incubadas durante 72 h em solução de polietilenoglicol (PEG, -2,04 MPa), posteriormente foram desidratadas em sílica gel (10% de teor de água) e reidratadas. A viabilidade celular foi avaliada pelo teste de TUNEL e através de microscopia eletrônica de transmissão em radículas que foram submetidas à secagem ou não. O TUNEL-positivo confirmou a degradação do DNA por meio da fluorescência dos núcleos nas células da radícula com cinco mm de comprimento e as avaliações ultraestruturais detectaram a perda da integridade do conteúdo celular nas radículas com 3 e 5 mm de comprimento e que não sobreviveram à desidratação a 10% de teor de água.

In situ DNA fragmentation during the re-establishment of desiccation tolerance in germinated seeds of Cedrela fissilis Vell.

“…Understanding why these germinated seeds do not tolerate different levels of drying could be helpful to understand desiccation tolerance. The underlying mechanisms of the death of germinated orthodox seeds are less understood than the empirical description of the radicle length and the moisture content attained (Masetto et al, 2016). This is supported by the comparative analysis of the changes in MC of the PEG-treated and untreated C. fissilis radicles, during pre-humidification (for 24 h) and the first 24 h of rehydration were similar ( Figure 1C).…”

Desiccation Tolerance and germination of Psidium guajava seeds from different regions of Brazil

“…The mechanisms involved in desiccation tolerance are gradually deactivated during germination, with a complete loss of tolerance for many species usually coinciding with radicle protrusion (Buitink et al, 2003;Bewley et al, 2013). Sometimes, DT loss happens after radicle protrusion, as has been observed in Sesbania virgata and Handroanthus impetiginosus (Vieira et al, 2010;Martins et al, 2015;Masetto et al, 2015;Costa et al, 2016). In both batches, the highest GSI values were observed after 9 days of imbibition followed by drying.…”

“…When seedlings become sensitive to desiccation, they are particularly vulnerable to water deficit effects (especially in the radicle region), which may lead to seedling death (Kalemba et al, 2019). Some protocols have been suggested to attempt at recovering DT in germinated seeds (Vieira et al, 2010;Masetto et al, 2014Masetto et al, , 2015, which could promote the survival of these individuals under natural selection.…”

Mechanistic insights derived from re-establishment of desiccation tolerance in germinating xerophytic seeds: Caragana korshinskii as an example

“…Caragana korshinskii is a member of the Fabaceae for which there have been around 50 sequenced genomes ( Sun et al., 2022 ). Furthermore, several seeds of species in Fabaceae relate to the study of seed DT like Pisum sativum , Sesbania virgate , Medicago truncatula , and V igna unguiculata ( Buitink et al., 2003 ; Leprince et al., 2004 ; Faria et al., 2005 ; Boudet et al., 2006 ; Buitink et al., 2006 ; Terrasson et al., 2013 ; Masetto et al, 2014 ; Masetto et al, 2016 ; Silva et al., 2017 ; Wang et al., 2021 ). Among them, DT in seeds of M. truncatula is well studied ( Buitink et al., 2003 ; Leprince et al., 2004 ; Faria et al., 2005 ; Boudet et al., 2006 ; Buitink et al., 2006 ; Terrasson et al., 2013 ).…”