Abstract: The transcription factors Flowering Locus C（FLC）and SHORT VEGETATIVE PHASE
（SVP）regulate the flowering time via protein interactions in the homologous plants of Brassica juncea or
Brassica oleracea，respectively. However，the heterologous protein-protein interactions between BoFLC of
Brassica oleracea and BjSVP of Brassica juncea have not been thoroughly understood. In an effort to
unravel the mechanisms involved in the heterologous interactions，we cloned BjSVPΔ1–BjSVPΔ11（MI，
MIK，K，IKC，KC，IK，IK1L1K2L2，IK1L1K2，IK1L1，IK1 or I domains）in Brassica juncea，BoFLC and BoFLCzq in Brassica oleracea，respectively. Then we tested the interactions between BoFLC and
BjSVP，using the Gal4 yeast two-hybrid system and the β-galactosidase activity assay. Results showed that
BjSVP or BjSVPΔ2 – BjSVPΔ5 interact with BoFLC. And the fused strains were incubated on
QDO/X-α-Gal/AbA plate and blue colonies were found，suggesting that the yeast fusion reporter genes
HIS3，AUR1-C，ADE2，and MEL1 were activated. It also indicated that the full length of K domain
（BjSVPΔ3）was the key amino acid region to independently mediate the protein interactions. However，
BjSVPΔ7–BjSVPΔ11 truncated forms without K1，K2，K3，L1 or L2 in K domain failed to act with
BoFLC. Furthermore，the heterologous interaction was enhanced by I domain of BjSVP，but weakened by
its M domain and C domain. The interaction also enhanced by BoFLC or BoFLCzq，compared with the
interaction of BjFLC protein. The three amino acid variations（site 20 of I domain，site 65 of K domain and
site 32 of C domain）were probably related to the protein interaction strength.

Key words: Brassica juncea, Brassica oleracea, FLC, SVP, truncated forms, yeast two-hybrid system