Gene expression analysis

To investigate the expression pattern of OsMYB36s, we sampled diverse tissues including root, stem, leaf blade, and leaf sheath tissue. The spatial expression pattern of OsMYB36s in roots was examined using different root segments (0–1, 1–2, 2–3, and 3–4 cm from the root apex) that were separately harvested from 5-day-old seedlings. Total RNA was extracted from the samples using a TRIzol reagent kit (Life Technologies, Carlsbad, CA, USA) and reverse-transcribed using a PrimeScript II 1st Strand cDNA Synthesis kit (Takara, Shiga, Japan) according to the manufacturer’s instructions. The expression of OsMYB36s was determined using ChanQ SYBR Color qPCR Master Mix (Vazyme) in a qTOWER version 2.0 system (Analytik Jena, Jena, Germany). Three biological replicates were analyzed per sample. Histone H3 was used as an internal control. The primers used for RT-qPCR are shown in Supplemental Data Set S8.