RNA-seq (Lexogen Quantseq 3) of P. alba x P. tremula (P.  canescens (Aiton) Sm. clone INRA 7171B4): 20-50% relative root tissue after 5 weeks: 20 mutant control condition
Based on the observation of root suberin deposition in control conditions, root zones of 20-50% relative distance that comprised the onset of SL development were harvested. To form one biological replicate, about six roots were pooled, frozen in liquid nitrogen, and ground (Retsch MM400, Retsch GmbH, Germany). Subsequent RNA isolation was performed following the manufacturers instructions (Zymo: Quick-RNA Miniprep) and sequencing was carried out on a NovaSeq 6000 system using a Lexogen QuantSeq 3-mRNA protocol.