甘蓝开花抑制因子FLC家族氨基酸序列差异及其对FLC/SVP聚合化的影响

Differences of FLC Family Members and Its Effect on Dimerization of FLC/SVP in Brassica oleracea

为深入研究甘蓝Flowering Locus C(FLC)家族与SHORT VEGETATIVE PHASE(SVP)蛋白互作的分子机理及其对开花的调控作用,从甘蓝‘ZQ-67’材料中克隆了5个FLC家族基因(记为BoFLCy1～BoFLCy5)。它们均编码MIKC型蛋白,按进化关系其编码蛋白可分为两类:BoFLCy3和BoFLCy5为第Ⅰ类,仅在C域有1个位点变异;BoFLCy1、BoFLCy2和BoFLCy4为第Ⅱ类,仅在K、C域分别有1、2个位点变异。酵母双杂交显示:甘蓝BoFLC家族蛋白均可与BoSVP蛋白互作;但BoFLCy4蛋白最为敏感,其N端插入3个氨基酸TET会破坏该作用。β–半乳糖苷酶活性分析表明:BoFLCy1～BoFLCy5与BoSVP互作强度差异显著,强弱关系为:BoFLCy1>BoFLCy2>BoFLCy3>BoFLCy5>BoFLCy4,该家族蛋白KC域内的变异位点若为疏水氨基酸则有利于FLC/SVP聚合。进一步分析突变BoFLCy4蛋白IK域内的保守位点发现:蛋白作用强度可能不受I域的这些保守性亲(疏)水氨基酸(第63、77位)影响,而会受到K域保守氨基酸(第120、121、135、157位)的亲(疏)水性调节。

The transcription factors Flowering Locus C(FLC)and SHORT VEGETATIVE PHASE(SVP)interact to delay the flowering time in the plants of Brassica oleracea,but the molecular mechanisms have not been thoroughly understood.In an effort to unravel the mechanisms of the protein interactions,five FLC genes(named BoFLCy1–BoFLCy5) were cloned in Brassica oleracea.And all the FLC family members encoded MIKC-type proteins which were classified into two groups.Group one has two members(BoFLCy3 and BoFLCy5)with only one variational amino acid in C domain.While group two has three members(BoFLCy1,BoFLCy2 and BoFLCy4)with one or two variational amino acid positions in K or C domain,respectively.Then yeast two-hybrid system was used in the experiments and showed that all the BoFLCs(BoFLCy1–BoFLCy5)could act with BoSVP protein,but the three amino acids of TET inserted into the N-terminal of BoFLCy4 may destroy the protein interaction.Furthermore,the β-galactosidase activities were tested and indicated that the relationships of significantly different strengths among BoFLCs/BoSVP were BoFLCy1>BoFLCy2>BoFLCy3>BoFLCy5>BoFLCy4.The hydrophobic amino acids,which lied in the variational positions in KC domains of BoFLCs,were helpful for the polymerization of FLCs/SVP.And the conservative amino acids,positions of 63,77,120,121,135 and 157 in IK domains of BoFLCy4,were respectively mutated and then acted with BoSVP protein.The results suggested that these hydrophilic or hydrophobic amino acids in K domain not in I domain regulated and affected the interaction strength.