library_construction_protocol: For each sample, 5 to 7 young but adult leaves from 6-week-old plants were used. These were placed in 50 µM ABA solution for 4h, i.e. the ABA was fed through the petiole. The EBCs of these leaves were collected with a spatula. Plants were grown in the greenhouse in soil under standard conditions. Total RNA was isolated using the the NucleoSpin RNA Plant Kit (Macherey-Nagel) according to the manual. In brief, the plant tissue was frozen with liquid nitrogen and homogenzied with mortar and pestle manually. 50mg of the frozen plant powder were mixed strongly with 350µl of the lysis buffer RA1 containing TCEP (1:100). The lysate was transferred to the NucleoSpin Filters and centrifuged for 1 min at 11,000 g. The filtrate was mixed with 350 µl 70% ethanol and transferred to the NucleoSpin RNA plant Column and centrifuged for 1 min at 11,000 g. The washing steps were performed following the manufacturer's instructions. RNA was eluted in 33 µl RNase free water that was incubated on the membrane twice for 1 min. Quality control measurements were performed on an Experion TM automated electrophoresis station (Bio-Rad Hercules, California, U.S.A.) and the concentration was determined using a Nanodrop ND-1000 spectrophotometer (Thermo Fisher Scientific, Wilmington, DE, U.S.A.). Library preparation and RNAseq were carried out as described in the Illumina TruSeq Stranded mRNA Sample Preparation Guide, the Illumina NextSeq 500 System Guide (Illumina, Inc., San Diego, CA, USA), and the KAPA Library Quantification Kit - Illumina/ABI Prism User Guide (Kapa Biosystems, Inc., Woburn, MA, USA). In brief, 250 ng of total RNA was used for purifying the poly-A containing mRNA molecules using poly-T oligo-attached magnetic beads. Following purification, the mRNA was fragmented to an average insert size of 200-400 bases using divalent cations under elevated temperature (94°C for 4 minutes). Next, the cleaved RNA fragments were reverse transcribed into first strand cDNA using reverse transcriptase and random hexamer primers. Actinomycin D was added to improve strand specificity by preventing spurious DNA-dependent synthesis. Blunt-ended second strand cDNA was synthesized using DNA Polymerase I, RNase H and dUTP nucleotides. The incorporation of dUTP, in place of dTTP, quenched the second strand during the later PCR amplification, because the polymerase does not incorporate past this nucleotide. The resulting cDNA fragments were adenylated at the 3' ends, the indexing adapters were ligated and subsequently specific cDNA libraries were created by PCR enrichment. The libraries were quantified using the KAPA SYBR FAST ABI Prism Library Quantification Kit.