Detailly , it was ( l ) to isolate and construct high efficiency expression vector of rice starch branching enzyme gene sbe2b and ( 2 ) to establish a high - effecient rice transformation system . total rna was extracted from maize endosperm 15dap ( days after pollination ) . and cdna of sbe2b was obtained through rt - pcr . sequencing result showed that the full length cdna was 2 . 4kbp , coding for 800 amino acids , with estimated mw 93kd 本研究從授粉15天左右的玉米胚乳中提取了總rna ,采用rt - pcr方法,克隆了玉米胚乳的淀粉分支酶基因sbe2b ,測序結果表明,玉米胚乳sbe2b的cdna全長為2 . 4kb ,編碼800個氨基酸,推測的氨基酸的分子量為93000d ,該序列與genbank中登錄號為af072725的玉米sbe2b的cdna序列有98的同源性,與水稻、大麥、小麥等禾本科植物的有關淀粉分支酶的dna序列都有極高的同源性。