Integrating guard cell metabolomics data with stomatal
speediness parameters
We next created a correlation-based network by combining guard cell
metabolite profiling data with stomatal speediness parameters
(Sl max and t50%). We further
integrated this with the previous multivariate analysis in order to
obtain a systemic view of the physiological and metabolic alterations
induced by NtSUS2 that could potentially modulate stomatal
speediness. Sixteen metabolites were found to be positively and
negatively correlated to Sl max and
t50%, respectively (Figure 8A). Five of those
metabolites (Ser, Ala, citrate, aconitate and mannitol) are also present
in the VIP scores and S-plots of PLS-DA and orthoPLS-DA models carried
out using relative guard cell metabolic changes during dark-to-light
transition (Figure 8A). These results indicate that these metabolites
are great contributors to the discrimination between the genotypes
observed in both PLS-DA and orthoPLS-DA models and are positively
correlated with the speed of light-induced stomatal opening. By
contrast, trehalose and adipic acid were negatively and positively
correlated to Sl max and t50%,
respectively (Figure 8A), indicating a negative correlation with the
light-induced stomatal opening speediness. Interestingly, the
metabolites that are positively and negatively related to the speed of
light-induced stomatal opening have respectively lower and higher
relative metabolic changes in both transgenic lines when compared to the
WT during dark-to-light transition (Figure 8B). Comparing the
dark-to-light transition in each genotype, it is interesting to note
that aconitate increased significantly only in the WT, while adipic acid
increase in all genotypes and mannitol decreased in L13 (Figure 8C). The
higher accumulation of aconitate in WT and the lower relative changes in
citrate observed in L3 further suggest that sucrose breakdown is
important to feed the C6-branch of the TCA cycle. Collectively, our
results suggest that NtSUS2 is important for guard cell
metabolism and, by consequence, for the regulation of light-induced
stomatal opening and WPT.