Involvement of phospholipases and sucrose in carbon starvation-induced non-chilling peel pitting in citrus fruit
Paco Romero, Fernando Alférez and María T. Lafuente
Postharvest Biology and Technology, Volume 169, November 2020, 111295
2020
บทคัดย่อ
The involvement of different isoforms of genes encoding phospholipases D (CsPLDα, CsPLDβ, CsPLDδ, CsPLDγ and CsPLDζ) and A2 (CsPLA2α, CsPLA2β and CsPAT1) on starvation-induced postharvest non-chilling peel pitting (NCPP) has been compared in the inner (albedo) and outer (flavedo) parts of the peel of citrus fruit treated or not with sucrose (Suc). The study has been performed in Navelate (Citrus sinensis (L.) Osbeck) sweet orange, which is prone to NCPP, stored under non-stressful environmental conditions (90–95 % relative humidity (RH) and 20 °C). Transcriptional changes, as well as respiration rate and ATP content evolution during fruit storage were compared in both peel tissues. Results indicated that the albedo is more susceptible than the flavedo to starvation; and that, at early stress stage, ATP and all CsPLD isoforms and CsPLA2β are good indicators of carbon starvation in the albedo, and CsPLDβ in the flavedo. These carbon starvation-induced signals were not activated when Suc was applied as an external energy source. In the second phase of starvation, expression of all CsPLD-encoding genes increased with NCPP; and CsPLDγ and CsPLDζ showed major increases in both peel tissues. The correlation of the expression of CsPLA isoforms with damage development was lower. In this phase, Suc may protect the fruit by providing additional energy sources to sustain respiration; and by favouring phospholipid-derived signaling messengers mediated by CsPLDβ and CsPAT1 in the albedo, CsPLDζ in the flavedo, and CsPLA2β in both tissues. Results from the examination of changes in gene expression point out tissue specificities in the expression of CsPL genes but also different susceptibility to starvation between the flavedo and the albedo in citrus fruit.