3.2 Microarray analysis of drought-stressed plants expressing
chloroplast Fld
Transcriptional profiling is a powerful experimental approach to
investigate plant responses to environmental challenges. Most
transcriptome analyses on water-restricted potatoes have been performed
on plants showing stress symptoms (Evers et al. 2010; Kondrák,
Marincs, Antal, Juhász & Bánfalvi 2012; Zhang et al. 2014). Fld
provided protection against drought effects occurring at a
pre-symptomatic stage that might contribute to the differential
tolerance exhibited by Fld-expressing plants. Therefore, a genome-wide
transcriptional profiling was carried out using WT and Stpfld 252
leaves sampled at 3 days of treatment as RNA source, together with their
corresponding watered controls. Once again, the Stpfld 252 line
was chosen because of its high levels of Fld accumulation and drought
protection.
Gene expression profiles were determined using a single-channel Agilent
potato microarray consisting of 42034 probes. We did not carry out any
filtering for potential redundant probes mapping the same transcript due
to the difficulties related to the highly heterozygous nature of potato
genomes, their polyploidy variance, the different accessions used the
microarray design, the reference genome sequencing and our current work.
Functional annotation was based on the Mapman ontology using the
GoMapman website resource (Ramšak et al. 2014). More than 80% of
the genes included in the microarray could be assigned to a functional
category. The total number of leaf-expressed genes that passed the
background correction and filtering processes (Materials and Methods)
was similar for the two genotypes under control conditions and
represented about 75% of the total genes present in the microarray.