Figure S1 FKF1 WT TOC1 EMF1 ZTL GI CO SOC1 FT elF4A PHYA PHYB CRY1 CRY2 RGA FLK LD FPA FLC GAI ACTIN7 mrn1 WTmrn1 Figure S1. Expression of genes related to flowering time in wild-type and mrn1 leaves. Total RNA was isolated form 3-week-old wild-type and mrn1 leaves and converted into first-strand cDNAs that were used as templates to PCR amplify transcripts of FKF1, TOC1, EMF1, ZTL, GI, CO, SOC1, FT, PHYA, PHYB, CRY1, CRY2, FLK, LD, FPA, FLC, GAI, and RGA with primers listed in Lim et al (2004). The elf4A (At3g13920) and ACTIN7 (At5g09810) genes were used as a control. Lim, M.H., Kim, J., Kim, Y.S., Chung, K.S., Seo, Y.H., Lee, I., Kim, J., Hong, C.B., Kim, H.J., Park, C.M. (2004) A new Arabidopsis gene, FLK, encodes an RNA binding protein with K homology motifs and regulates flowering time via FLOWERING LOCUS C. Plant Cell, 16, 731–740. Clock genes Photoperiod genes Photoreceptors genes Autonomous genes GA genes

At5g42590At5g42610At5g42620 At5g42600 (MRN1) 1kb (a) RB LB T-DNA (b) Salk_ Figure S2 MRN1 ACTIN2 mrn1WT Figure S2. Mapping of T-DNA insertion sites and expression in MRN1 gene. (a) Structure of MRN1 (At5g42600) and T-DNA insertion site. Boxes and lines indicate exon and intron of the MRN1 gene, respectively. Arrows indicate the sites for specific primers, which were used in RT-PCR analysis. (b) RT-PCR analysis of MRN1 gene in wild-type and mrn1 roots. Total RNA was isolated form wild-type and mrn1 roots and 100 ng of total RNA was used in RT-PCR analysis. The ACTIN2 (At3g18780) gene was used as a control.

KRP1 KRP2 KRP3 KRP4 KRP5 CycB1;2 CycD3;1 ACTIN7 mrn1WT Figure S3. Expression of cell-cycle related genes in Arabidopsis wild-type and mrn1 leaves. Total RNA was isolated from 3-week-old wild-type and mrn1 leaves and were converted into first-strand cDNAs that were used as templates to PCR amplify transcripts of KRP1, KRP2, KRP3, KRP4, KRP5, KRP6, KRP7, CycB1;2, and CycD3 genes with specific primers listed in Table S2 online. The Actin7 (At5g09810) gene was used as a control. Figure S3

Figure S4 FK SMT2 DWF7 DWF5 CYP710A1 DWF1 DWF6 DWF4 DWF3 BR6ox1 CYP710A2 ACTIN7 mrn1WT Figure S4. Expression of BR and sterol metabolic genes in wild-type and mrn1 roots (a) and leaves (b). Total RNA was isolated from 2~3 weeks old roots and leaves in Arabidopsis wild-type and mrn1 plants and converted into first-strand cDNAs that were used as templates to PCR amplify transcripts of BR and sterol metabolic genes (FK, SMT2, DWF7, DWF5, DWF1, DWF6, DWF4, DWF3, BR6ox1, CYP710A1, CYP710A2) with specific primers listed in Table S3. The ACTIN7 (At5g09810) gene was used as a control. ( b ) FK SMT2 DWF7 DWF5 CYP710A1 DWF1 DWF6 DWF4 DWF3 BR6ox1 CYP710A2 ACTIN7 mrn1WT ( a )

 -Sitosterol 2,3-Oxidosqualene Cycloartenol Brassinolide Marnerol MRN1 Lanosterol LAS1CAS1 LUP1  AS1 Lupeol +  - Amyrin Acetyl-CoA HMG-CoA MVA squalene SQE HMGR Primary metabolism Secondary metabolism O HO H H H H H H H H H H H OH H H H H O O H H H H HO H H H (Marneral) Figure S5. The simplified biosynthetic pathways of sterol, steroid hormone, and nonsteroidal triterpenoids in plants. Abbreviations: HMG-CoA, 3-hydroxy-3- methylglutaryl-CoA; HMGR, 3-hydroxy-3-methylglutaryl-CoA reductase; LUP1, lupeol synthase; MRN1, marneral synthase; MVA, mevalonate; SQE, squalene epoxidase;  AS1,  -amyrin synthase. Figure S5 H