3.9 Drought-responsive genes primed by Fld expression
Clusters 14-17 included DE transcripts that responded to water
limitation but were also modulated by Fld in the same direction under
normal growth conditions (Figure 6c, Supplementary Table S9). Cluster 14
contained 76 transcripts that were induced by chloroplast Fld to the
levels attained in drought-stressed WT plants, while genes grouped in
cluster 15 (35 members) were further up-regulated by water limitation in
both WT and Stpfld 252 plants. DE genes over-represented in these
clusters belonged to the ethylene and minor carbohydrate functional
categories, including a myo-inositol-1-phosphate synthase (MIPS) that
catalyzes the first step of myo-inositol biosynthesis.
Cluster 16 comprised 127 genes whose expression was repressed by Fld
under growth chamber conditions to the levels attained by the drought
treatment in both lines (Figure 6c, Supplementary Table S9). Most
conspicuous among them was the ethylene responsive factor 5 (ERF5).
Finally, cluster 17 included 52 transcripts that were repressed by
chloroplast-targeted Fld in the absence of stress, and further by
drought in both lines (Figure 6c, Supplementary Table S9), with no
specifically enriched functional category.