3.4.1 Changes in sugar levels during SL
We were interested to know whether the high sucrose levels in
CO2 -treated strawberries during LT storage were
preserved during SL. Higher levels of sucrose were quantified in LTC
relative to SLC. Sucrose content was also 50% higher than in LTA
(Figure 6 A), reaching values of 6.2±0.5 mg g-1 FW.
However, no significant differences in glucose or fructose levels were
found in LTC when compared to SLC and LTA (Figures 6 B-C). On the other
hand, a slight yet significant increase in myo-inositol was found in LTC
in comparison with SLC, with lower levels of trehalose being seen in
both LTA and LTC (Figure 6 D). Asides from a slight decrease in
1-kestose during LTC, no significant differences in FOS or raffinose
were quantified when values were compared during SL (Figures 6 F-J). The
higher levels of estaquiose quantified in air-stored fruit during
storage at 0 ºC seems to be maintained after transfer to 20 ºC (Figure 6
K). The highest level of estaquiose, therefore, was quantified in LTA.
3.4.2 Changes in the expression of genes involved in
sucrose metabolism during SL
Expression of the main genes involved in sucrose metabolism was analysed
in order to identify whether transcriptional regulation of these genes
changes in response to SL. A decrease in FvSPS1 , the main
homologue expressed, was observed in LTA strawberries when compared with
SLC and LTC (Figure 7 A). Moreover, a significant decrease inFvSS1 expression was found in the main homologue expressed in LTA
and LTC, compared with SLC (Figure 7 B). Thus, these results seem to
indicate that CO2 pre-treatment maintains sucrose
synthesis after transfer to 20 ºC, whereas LT reduces sucrose breakdown.
Changes in the relative gene expression of invertases during SL are
indicated in Figures 7 C and D. Interestingly, whilst no changes toFvCWINV homologues were observed, a significant decrease in the
expression of both FvVINV homologues was quantified in LTC
compared to SLC. Furthermore, FvVINV2 expression was found to
significantly increase during LTA. These results indicate that
CO2 pre-treatment significantly reduces sucrose
degradation during SL. Overall, the present analysis of gene expression
could explain the high level of sucrose detected in LTC during SL.