Transposon insertion resulted in the silencing of Wx-B1n in Chinese wheat landraces.
A novel Wx-B1 allele was characterized; a transposon insertion resulted in the loss of its function, which is different from the previously reported gene silencing mechanisms at the Wx-B1 locus. The waxy protein composition of 53 Chinese wheat landraces was analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional gel electrophoresis; of these, 10 did not show the expression of Wx-A1 (four accession) or Wx-B1 (six accessions) protein. The results of molecular marker detection revealed that the Wx-B1 allele (Wx-B1n) showed normal expression, inconsistent with the findings of SDS-PAGE for the Xiaobaipi accession. Further cloning of the 9160-bp region covering the Wx-B1 coding region and 3'-downstream region revealed that a 2178-bp transposon fragment had been inserted at 2462 bp within the tenth exon of Wx-B1n ORF, leading to the absence of Wx-B1 protein. Sequence analysis indicated that the insertion possessed the structural features of invert repeat and target repeat elements, we deduced that it was a transposon. Further PCR analysis revealed that this fragment had moved, but not copied itself, from 3B chromosome to the current location in Wx-B1n. Therefore, the reason for the inactivation of Wx-B1n was considerably different from those for the inactivation of Wx-B1b, Wx-B1k, and Wx-B1m; to our knowledge, this kind of structural mutation has never been reported in Wx-B1 alleles. This novel allele is interesting, because it was not associated with the deletion of other quality-related genes included in the 67 kb region lost with the common null allele Wx-B1b. The null Wx-B1n might be useful for investigating gene inactivation and expression as well as for enriching the genetic resource pool for the modification of the amylose/amylopectin ratio, thereby improving wheat quality.
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Ling-Ling
LL
Zhang
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Hu
H
Chen
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Mi
M
Luo
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Xiao-Wei
XW
Zhang
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Mei
M
Deng
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Jian
J
Ma
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Peng-Fei
PF
Qi
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Ji-Rui
JR
Wang
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Guo-Yue
GY
Chen
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Ya-Xi
YX
Liu
College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Zhi-En
ZE
Pu
College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Wei
W
Li
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Xiu-Jin
XJ
Lan
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
Yu-Ming
YM
Wei
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
You-Liang
YL
Zheng
Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China. qiantaojiang@sicau.edu.cn.
Qian-Tao
QT
Jiang
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D016386:Chromosome Walking; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D020868:Gene Silencing; D017343:Genes, Plant; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames; D010940:Plant Proteins / Q000235:genetics; D013214:Starch Synthase / Q000235:genetics*; D014908:Triticum / Q000201:enzymology / Q000235:genetics*
D004251:DNA Transposable Elements; D010940:Plant Proteins; D013214:Starch Synthase