Starch branching enzyme II of potato

Abstract

The present invention relates to an amino acid sequence of second starch branching enzyme (SBE II) of potato and a fragment thereof as well as to the corresponding isolated DNA sequences. Furthermore, the invention relates to vectors comprising such an isolated DNA sequence, to processes for production of transgenic potatoes, and to the use of said potatoes for the production of starch. The starch obtained will show a changed pattern of branching of amylopectin as well as a changed amylose/amylopectin ratio.

We claim:  
     
         1 . An amino acid sequence of potato starch branching enzyme II (SBE II) comprising the amino acid sequence as shown in SEQ ID No. 1.  
     
     
         2 . Fragments of the amino acid sequence of potato starch branching enzyme II (SBE II), capable of affecting the amylose/amylopectin ratio in potato starch, as well as reducing or changing the pattern of the branching of amylopectin.  
     
     
         3 . A fragment according to  claim 2 , having the amino acid sequence as shown in SEQ ID No. 2.  
     
     
         4 . An isolated DNA sequence encoding starch branching enzyme II (SBE II) of potato comprising the nucleotide sequence as shown in SEQ ID No. 1, and variants thereof resulting from the degeneracy of the genetic code.  
     
     
         5 . Fragments of the isolated DNA sequence, as shown in SEQ ID No. 1 and encoding starch branching enzyme II (SBE II) of potato, which fragments are capable of affecting the amylose/amylopectin ratio in potato as well as reducing or changing the pattern of the branching of amylopectin.  
     
     
         6 . Fragments according to  claim 5  comprising 50-3074 bp of the nucleotide sequence as shown in SEQ ID No. 1, and variants thereof resulting from the degeneracy of the genetic code.  
     
     
         7 . A fragment according to  claim 5 , comprising the nucleotide sequence as shown in SEQ ID No. 2.  
     
     
         8 . A vector comprising the whole or a functionally active part of the isolated DNA sequence according to  claim 4  and regulatory elements active in potato.  
     
     
         9 . A vector comprising the whole or a functionally active part of the isolated DNA sequence according to  claim 5  and regulatory elements active in potato.  
     
     
         10 . A vector comprising the whole or a functionally active part of the isolated DNA sequence according to  claim 6  and regulatory elements active in potato.  
     
     
         11 . A vector comprising the whole or a functionally active part of the isolated DNA sequence according to  claim 7  and regulatory elements active in potato.  
     
     
         12 . A vector according to  claim 8 , wherein the DNA sequence is in the antisense (reversed) orientation in relation to a promoter immediately upstream from the DNA sequence.  
     
     
         13 . A process for the production of transgenic potatoes with either an increased or a decreased degree of branching of amylopectin starch, characterized in that it comprises the following steps: 
 a) transfer and incorporation of a vector according to  claim 8  into the genome of a potato cell, and    b) regeneration of intact, whole plants from the transformed cells.    
     
     
         14 . A process for the production of transgenic potatoes with a reduced degree of branching of amylopectin starch, characterized in that it comprises the following steps: 
 a) transfer and incorporation of a vector according to  claim 12  into the genome of a potato cell, and    b) regeneration of intact, whole plants from the transformed cells.    
     
     
         15 . A process according to  claim 14 , wherein the vector also comprises an antisense construct of starch branching enzyme I (SBE I).  
     
     
         16 . A process according to  claim 14 , wherein the vector also comprises an antisense construct of potato granule bound starch synthase II.  
     
     
         17 . A process according to  claim 15 , wherein the vector also comprises an antisense construct of potato granule bound starch synthase II.  
     
     
         18 . A process according to  claim 14 , wherein the vector also comprises an antisense construct of potato soluble starch synthases II and III.  
     
     
         19 . A process according to  claim 15 , wherein the vector also comprises an antisense construct of potato soluble starch synthases II and III.  
     
     
         20 . A process according to  claim 16 , wherein the vector also comprises an antisense construct of potato soluble starch synthases II and III.  
     
     
         21 . A process according to  claim 14 , wherein the vector also comprises an antisense construct of potato starch disproportionating enzyme (D-enzyme).  
     
     
         22 . A process according to  claim 15 , wherein the vector also comprises an antisense construct of potato starch disproportionating enzyme (D-enzyme).  
     
     
         23 . A process according to  claim 16 , wherein the vector also comprises an antisense construct of potato starch disproportionating enzyme (D-enzyme).  
     
     
         24 . A process according to  claim 18 , wherein the vector also comprises an antisense construct of potato starch disproportionating enzyme (D-enzyme).  
     
     
         25 . A process according to  claim 14 , wherein the vector also comprises an antisense construct of potato starch debranching enzyme.  
     
     
         26 . A process according to  claim 15 , wherein the vector also comprises an antisense construct of potato debranching enzyme.  
     
     
         27 . A process according to  claim 16 , wherein the vector also comprises an antisense construct of potato debranching enzyme.  
     
     
         28 . A process according to  claim 18 , wherein the vector comprises an antisense construct of potato debranching enzyme.  
     
     
         29 . A process according to  claim 21 , wherein the vector also comprises an antisense construct of potato debranching enzyme.  
     
     
         30 . A transgenic potato obtainable by the process according to  claim 13 .  
     
     
         31 . A transgenic potato obtainable by the process according to  claim 14 .  
     
     
         32 . A transgenic potato obtainable by the process according to  claim 15 .  
     
     
         33 . A transgenic potato obtainable by the process according to  claim 16 .  
     
     
         34 . A transgenic potato obtainable by the process according to  claim 18 .  
     
     
         35 . A transgenic potato obtainable by the process according to  claim 21 .  
     
     
         36 . A transgenic potato obtainable by the process according to  claim 25.