2.1 Plant Growth Conditions
Non-transgenic rice (Oryza sativa L. cv. Nipponbare), CRCT overexpression line (driven by Actin promoter; Morita et al. 2015), FLAG-CRCT overexpression line, and CRCT knockout line were grown in paddy soil under natural light conditions in a temperature-controlled greenhouse (30°C day/25°C night). Rice seedlings at the 4.5 leaf stage were transplanted into 1 L pots supplemented with 2.0 g chemical fertilizer (N:P:K=8:8:8), 0.5 g slow-release fertilizer, 0.15 g micronutrient, and 1.5 g silicate fertilizer. For qRT-PCR and starch content analyses, the seedlings of six rice cultivars (Nipponbare, Koshihikari, Habataki, Takanari, Momiroman, Leafstar) were transplanted into 1/5000 Wagner pots supplemented with 0.6 g N chemical fertilizer, 1.0 g slow-release fertilizer, 0.4 g micronutrient, and 4.0 g silicate fertilizer per pot. These plants were grown under natural light and temperature in a net house. The leaf blade and leaf sheath were sampled at 18:00-19:00 (photoperiod of 5:00-19:00) on sunny days, immediately frozen in liquid nitrogen and stored at -80°C until required.