白桦BpTOPP1基因功能

A Preliminary Study on Function of BpTOPP1 Gene in Betula platyphylla × B. pendula

为揭示白桦(B.platyphylla×B.pendula)中BpTOPP1基因的功能,以欧洲白桦和裂叶桦为试材,采用qRT-PCR方法开展BpTOPP1时空表达特性分析,同时克隆BpTOPP1基因并构建植物表达载体,通过白桦合子胚转化技术获得BpTOPP1过表达株系。结果表明:BpTOPP1是编码313个氨基酸的蛋白,包含942 bp的开放阅读框,含4个外显子和3个内含子。BpTOPP1基因在欧洲白桦和裂叶桦中的表达量不尽相同,欧洲白桦中该基因的组织部位表达特性在第2片叶中表达量呈现上调表达,是芽的2.04倍;时序表达特性分析中该基因在7月21日时的表达量显著高于裂叶桦。裂叶桦中BpTOPP1基因在组织部位表达特性分析发现,该基因主要在叶柄呈现上调表达;时序表达特性分析发现该基因的表达量在5月5日和8月22日时显著高于欧洲白桦。BpTOPP1过表达转基因株系与野生型对照白桦(WT)比较,转基因株系出现叶片延迟脱落、叶柄表皮毛变多、植株矮化和叶片变小现象;转基因株系的苗高均值仅为野生型对照白桦的80.28%,叶面积仅为野生型对照白桦的57.8%,叶绿素相对含量调查显示,转基因株系TO-2、TO-4、TO-5和TO-6等4个转基因株系显著高于野生型对照白桦,初步判断BpTOPP1基因在白桦叶片的生长和发育中起关键作用。

To reveal gene function of BpTOPP1 in Betula platyphylla ×B. pendula,we analyzed gene expression pattern of BpTOPP1 by qRT-PCR. We used B. pendula and B. pendula‘Dalecarlica＇ in this study. The open reading frame（ ORF） of BpTOPP1 was 942 bp in length,encoded a putative 313-amino acid protein. The cD NA fragment of BpTOPP1 was cloned and plant expression vector was constructed for birch gene transformation. The expression pattern of BpTOPP1 in B. pendula and B. pendula‘Dalecarlica＇ plants was different. The expression level of BpTOPP1 in the second leaf of Betula pendula was 2.04 times higher than its buds. On July 21,BpTOPP1 was significantly enriched in Betula pendula than B. pendula‘Dalecarlica＇. The expression of BpTOPP1 was mainly enriched in the petiole of B. pendula‘Dalecarlica＇,and was significantly higher than B. pendula both on May 5 and August 22. Compared with Wild type birch（ WT）,BpTOPP1 overexpression transgenic lines showed phenotypes of delayed leaf shedding,more petiole epidermis,dwarfing plants and smaller leaves. The transgenic lines were 80.28% shorter in height and 57.8% smaller in leaf area than those of WT. The relative chlorophyll content of TO-2,TO-4,TO-5 and TO-6 transgenic lines＇ leaves was significantly higher than WT. Our results indicate that BpTOPP1 gene may play a key role in tree growth and development of leaves.