3.3 Chloroplast Fld affected gene expression patterns of potato
leaves in the absence of stress
We first evaluated the effect of chloroplast Fld on gene expression in
leaves of potato plants grown under normal conditions. Analysis of
transcript levels in WT and Stpfld 252 leaves showed that 1097
genes were induced 2-fold or more by Fld relative to WT siblings, with
181 increasing more than 4-fold in their expression. Also, 578
transcripts declined to 50% or less in Stpfld 252 leaves compared
to the wild type, 54 of which accumulated below or equal to 25% (Figure
3, Supplementary Table S2). Functional enrichment analysis of these DE
transcripts showed that among the genes induced in Stpfld 252
plants there was a remarkable over-representation of those associated to
protein degradation by the proteasome (Figure 3, Supplementary Table
S2). It is worth noting that a similar induction pattern has been
observed in Fld-expressing tobacco plants (Pierella Karlusich et
al. 2017), indicating that plastid-located Fld exerts a key regulatory
role in the accumulation of proteasomal components in different species,
presumably through modulation of chloroplast redox chemistry.
Functional categories that displayed differential repression by Fld
comprised trehalose synthesis, nitrate metabolism, amino acid
degradation and traits associated to metal uptake and utilization such
as Cd- and Al-induced proteins, Cu chaperones and Fe-chelate reductases.
Noteworthy, ethylene metabolism and signaling were consistently
down-regulated in Stpfld 252 plants, including 29 genes encoding
transcription factors of the apetala2/ethylene-responsive family (Figure
3, Supplementary Table S2). These observations also agree with earlier
reports on Fld-expressing tobacco plants (Pierella Karlusich et
al. 2017). The mechanisms underlying this repression are unknown and
deserve further investigation.