Proline is an α-amino acid that is used in the biosynthesis of
proteins. Some studies have shown that proline has been accumulated in plants
in response to biotic and abiotic stresses. Exogenous proline has thus been
used for improving some plant cryopreservation protocols. Further enhancement
of cryopreservation efficiency for in vitro grapevines could
be expected if stresses linked to cryopreservation procedures could be reduced.
In this study, the authors studied the possible beneficial effect of proline in
grapevine cryopreservation.
Single-node
explants from in vitro grown grapevine plantlets (Vitis
vinifera L. cv Portan) were cultured on shooting media (half-strength
MS + 1 μM BAP) containing no proline (control) or 50, 500, or 2000 μM
filter-sterilized L-proline. Shoot tips excised from these microshoots were
subjected to a PVS2-based droplet-vitrification procedure. Control and rewarmed
explants were grown on a recovery medium containing 1 μM BAP.
The results
demonstrated that shoot development on control medium and lower proline
concentrations did not notably differ whereas the highest concentration of
proline inhibited shoot development. Carry-over effects were observed since
lower survival and regrowth were obtained both for non-frozen or LN-treated
explants excised from micro-shoots obtained on the 2000 μM proline medium. No
significant differences in survival and regrowth were observed for non-frozen
explants subjected to pretreatment without LN exposure. A slightly enhancing
effect (although non-significant) on post-cryopreservation survival was
observed for explants derived from shoots developed on 50 or 500 μM
proline, but no significant improvement of regrowth percentage was observed for
these two conditions. Although a slight increase in survival could be observed,
no significant beneficial effect of proline pretreatment on
post-cryoconservation regrowth could be evidenced in the conditions. However,
the 2-week period before explant excision could have allowed at least partial
metabolism and catabolism of exogenous proline; the results observed could thus
have been the consequence of complex interactions.
In conclusion, shorter
proline treatments applied closer to the actual LN exposure step might produce
different results and allow for clearer interpretation.
Article by Zvjezdana
Marković, et al, from Croatia and France.
Full access: http://mrw.so/3x5AMU
Image by Christine Lomerio, from
Flickr-cc.
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