Mol Genet Genomics (2015)290:239-255 251 a60 b 45 55 5.37 43.11 0 3 15 OCK 15 OCK ■GAMh ■SA4h GA12h SA12h 0 023 C50 d e 75 10 745 78307725 70 南3857 520 25 OCK ■Cold4h ■ABA4h aHeat4h Cold12h 10 Fig.8 The relative expression ratio of BrMIKC genes under abiotic stresses.a GA:b SA:cABA:d cold;e heat.Error bars represent standard errors from three independent replicates 12 h.Because of the many BrMIKC genes and their com- Under heat stress,the expression levels of five BrMADS plicated expression changes,only some were selected for genes were upregulated;among these genes,BrMADS063, further analysis(Fig.8). AGL17 and BrMADS050,SVP had a higher expression lev- Three TM3-like ortholog BrMADS genes (BrMADS043, els at 4 h than at 12 h.Interestingly,BrMADS043,SOC; BrMADS036 and BrMADS041)were upregulated at 4 BrMADS019,CAL and BrMADS036,SOC had opposite and 12 h under GA treatment.The remaining six genes results. (BrMADS050.SVP:079,FLC:096,MAF;077,FLC; From the results above,45 duplicated genes were found 078,FLC and 104,MAF)had no response to GA (Fig.8a). in the Chinese cabbage MADS-box gene family(Fig.5 and Under SA treatment,BrMADS023,043,and 041,which are Supplementary Fig.8).Based on the expression levels of TM3-like ortholog genes,were upregulated at 4 and 12 h.these genes (34 BrMIKC genes)under different stresses BrMADS079,FLC;096,MAF:104,MAF;078,FLC;077, in Chinese cabbage,a line chart was used to show the FLC and 100.MAF were found with no response to SA different trends among them (Fig.9 and Supplementary treatment(Fig.8b). Table 13).Interestingly,we found four gene pairs with Under the other three abiotic stress treatments,most similar expression,including BrMADS (008:009;034:035; BrMADS genes have relatively low expression levels 017:015;077:079).Finally,the comparison of expression (Fig.7b),whereas several genes were significantly upregu- profiles of the duplicated gene pairs revealed that most lated in these different treatment conditions (Fig.8c-e). duplicated genes had diverged significantly in expression Under cold stress,the MAF ortholog,BrMADS gene level except for the above-mentioned four gene pairs. BrMADS100,was found with a high expression at 4 h but was downregulated at 12 h.The expression of two BrMADS genes (BrMADS001,AG and 023,SOC)was over Discussion 20 times that of the control at 4 and 12 h.In contrast,two genes (BrMADS043,SOC and 036,SOC)were downregu- Chinese cabbage is one of the most important vegetables lated at 4 and 12 h.Under ABA stress,the relative expres- that are cultivated worldwide.For successful breeding of sion levels of six BrMADS genes (BrMADS063,AGL17; biennial plants like Chinese cabbage,flowering time and BrMADS043,SOC:BrMADS083.AGL18;BrMADS050, floral organ development are important traits.MADS-box SVP;BrMADS036,SOC and BrMADS041,SOC)were genes are important regulators of both flowering and flo- upregulated at 4 h and then decreased rapidly at 12 h. ral organ development,and are thus key factors for the ②SpringerMol Genet Genomics (2015) 290:239–255 251 1 3 12 h. Because of the many BrMIKC genes and their com￾plicated expression changes, only some were selected for further analysis (Fig. 8). Three TM3-like ortholog BrMADS genes (BrMADS043, BrMADS036 and BrMADS041) were upregulated at 4 and 12 h under GA treatment. The remaining six genes (BrMADS050, SVP; 079, FLC; 096, MAF; 077, FLC; 078, FLC and 104, MAF) had no response to GA (Fig. 8a). Under SA treatment, BrMADS023, 043, and 041, which are TM3-like ortholog genes, were upregulated at 4 and 12 h. BrMADS079, FLC; 096, MAF; 104, MAF; 078, FLC; 077, FLC and 100, MAF were found with no response to SA treatment (Fig. 8b). Under the other three abiotic stress treatments, most BrMADS genes have relatively low expression levels (Fig. 7b), whereas several genes were significantly upregu￾lated in these different treatment conditions (Fig. 8c–e). Under cold stress, the MAF ortholog, BrMADS gene BrMADS100, was found with a high expression at 4 h but was downregulated at 12 h. The expression of two BrMADS genes (BrMADS001, AG and 023, SOC) was over 20 times that of the control at 4 and 12 h. In contrast, two genes (BrMADS043, SOC and 036, SOC) were downregu￾lated at 4 and 12 h. Under ABA stress, the relative expres￾sion levels of six BrMADS genes (BrMADS063, AGL17; BrMADS043, SOC; BrMADS083, AGL18; BrMADS050, SVP; BrMADS036, SOC and BrMADS041, SOC) were upregulated at 4 h and then decreased rapidly at 12 h. Under heat stress, the expression levels of five BrMADS genes were upregulated; among these genes, BrMADS063, AGL17 and BrMADS050, SVP had a higher expression lev￾els at 4 h than at 12 h. Interestingly, BrMADS043, SOC; BrMADS019, CAL and BrMADS036, SOC had opposite results. From the results above, 45 duplicated genes were found in the Chinese cabbage MADS-box gene family (Fig. 5 and Supplementary Fig. 8). Based on the expression levels of these genes (34 BrMIKC genes) under different stresses in Chinese cabbage, a line chart was used to show the different trends among them (Fig. 9 and Supplementary Table 13). Interestingly, we found four gene pairs with similar expression, including BrMADS (008:009; 034:035; 017:015; 077:079). Finally, the comparison of expression profiles of the duplicated gene pairs revealed that most duplicated genes had diverged significantly in expression level except for the above-mentioned four gene pairs. Discussion Chinese cabbage is one of the most important vegetables that are cultivated worldwide. For successful breeding of biennial plants like Chinese cabbage, flowering time and floral organ development are important traits. MADS-box genes are important regulators of both flowering and flo￾ral organ development, and are thus key factors for the Fig. 8 The relative expression ratio of BrMIKC genes under abiotic stresses. a GA; b SA; c ABA; d cold; e heat. Error bars represent standard errors from three independent replicates