B5 medium

The Arabidopsis T-DNA insertion lines mtp8-2 (SALK_140266), mtp9 (SALK_093515), mtp10 (SALK_121470 C), and mtp11 (SALK_025271 C) were obtained from ABRC. Homozygous lines were identified by PCR using the left border T-DNA-specific and the gene-specific primers (Supplementary Table S1). Seeds were surface sterilized in 70% ethanol, 0.05% Triton X-100, and then imbibed in sterile distilled 0.1% agarose at 4 °C for 3–5 days. Plants were grown on full or half strength B5 medium (Sigma). MnSO₄ was added from 100 mM stocks. For soil-grown plants, seeds were imbibed in sterile distilled 0.1% agarose at 4 °C for 3–5 days, and then sown directly onto autoclaved potting mix (MetroMix 820). Growth conditions for both plate-grown and soil-grown plants were 16 hour light, 8 hour dark at 22 °C.

Catharanthus roseus, Vinca Little Bright Eye¹, was used for this work. Seeds were surface sterilized and then germinated on B5 medium (Sigma, St. Louis, MO, USA) supplemented with Gamborg’s vitamins (Sigma, St. Louis, MO, USA). Seeds were germinated in the dark at 26°C for 2 weeks. The seedlings were then transferred to a 16-h-light/8-h-dark cycle with a light intensity of approximately 44 μmol m^-2 s^-1 for 4 weeks before inoculation with Agrobacterium tumefaciens.