Plant materials and plant growth
Arabidopsis thaliana seeds were surface sterilized and sown on 0.8% (w/v) agar plates containing ½ strength Murashige and Skoog media (Caisson Labs), 50mM MES-KOH, pH 5.7, and 1% (w/v) sucrose. Plants used for fluorometric measurements were germinated and cultivated on MS plates without sucrose. Following 2-3 days of stratification at 4°C, the plates were exposed to 100 μE m-2s-1 of light provided by cool white (4100K) fluorescent bulbs on a 12 h light/12 h dark cycle for 7-14 days at 22°C, at which point seedlings were transplanted to a soil-less mix (Fafard Germinating Mix, Sungro Horticulture), watered with 10% Hoagland’s solution (Hoagland and Arnon, 1950), and grown under the same conditions as the plates.
Columbia-0 ecotype was used as wild-type for all pictures and measurements in this study. Seeds for the T-DNA insertional mutants were acquired from the Arabidopsis Biological Resource Center (https://abrc.osu.edu/). Mutant alleles previously characterized as resulting in loss of function were used for the genetic crosses:get3b-2 ( SALK_017702C, Xing et al., 2017), cpsrp54-3 (WiscDsLox289_292B14, Yu et al., 2012), alb4-1 (SALK_136199, Bédard et al., 2017), stic2-3 (SALK_001500, Bédard et al. 2017 ) and stic2-4 ( WiscDsLox445D01, Bédard et al. 2017 ). The two stic2 alleles behaved similarly; therefore, we refer tostic2 mutants without the allele number in other sections of the paper. Lines carrying the mutant alleles were identified by PCR genotyping using the genotyping primers listed in Supplemental Table S2.