Arabidopsis Meristem Sample Prep and in situ Hybridization

Sample preparations including harvesting, fixing and embedding were performed as described [98 (link)]. Briefly, meristems of Arabidopsis (Col-0) plants were harvested, fixed and embedded in wax using an automated tissue processor (ASP200S; Leica, Wetzlar, Germany) and embedding system (HistoCore Arcadia; Leica, Wetzlar, Germany). Tissue sections of 8 μm thickness were prepared using a Leica RM2265 rotary microtome. Hybridization probes were synthesized using a Digoxigenin RNA Labelling kit (Roche, Mannheim, Germany) employing PCR products of whole open reading frames of the target genes. RNA in situ hybridizations were performed as described [111 (link)]. Primer sequences used in this analysis are given in Supplementary Table S1.