Identification of multiple highly similar XIP-type xylanase inhibitor genes in hexaploid wheat.
In hexaploid wheat, Xip-I is the only XIP-type xylanase inhibitor gene whose expression and function have been characterized in detail. Here we demonstrate the existence of new XIP-type genes with the identification of Xip-R1 and Xip-R2 in the root cDNAs. Southern blot analysis with the Xip-R1 probe revealed that XIP-type genes comprised a significantly greater gene family than previously speculated on in studies with the Xip-I probe. The transcript level of Xip-R genes was increased upon an inoculation with Erysiphe graminis in the leaves, but not with Fusarium graminearum in the spikelets. RT-PCR with the RNA samples followed by extensive sequencing of the cloned amplified products revealed the presence of 12 highly similar Xip-R genes. Among these genes, Xip-R1 was the only predominant Xip-R family member induced to express in response to E. graminis. XIP-R1 was located in the apoplastic space and inhibited family 11 xylanases, but the protein did not show chitinolytic activity. These results suggest that hexaploid wheat has a large family of XIPs in its genome, but that only some of them are expressed for plant defense in limited tissues.
Takahashi-Ando
Naoko
N
Plant & Microbial Metabolic Engineering Research Unit and Laboratory for Remediation Research, Discovery Research Institute (DRI) and Plant Science Center (PSC1), RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Inaba
Makiko
M
Ohsato
Shuichi
S
Igawa
Tomoko
T
Usami
Ron
R
Kimura
Makoto
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D018744:DNA, Plant; D043364:Endo-1,4-beta Xylanases / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D017343:Genes, Plant; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics; D030821:Plants, Genetically Modified; D011123:Polyploidy; D013347:Subcellular Fractions / Q000378:metabolism; D014908:Triticum / Q000235:genetics*
D018744:DNA, Plant; D004791:Enzyme Inhibitors; D043364:Endo-1,4-beta Xylanases