Scheible W R, Eshed R, Richmond T, Delmer D, Somerville C
Department of Plant Biology, Carnegie Institution, Stanford, CA 94305-4150, USA.
Proc Natl Acad Sci U S A. 2001 Aug 28;98(18):10079-84. doi: 10.1073/pnas.191361598. Epub 2001 Aug 21.
In many higher plants, cellulose synthesis is inhibited by isoxaben and thiazolidinone herbicides such as 5-tert-butyl-carbamoyloxy-3-(3-trifluromethyl) phenyl-4-thiazolidinone. Semidominant mutations at the IXR1 and IXR2 loci of Arabidopsis confer isoxaben and thiazolidinone resistance. Isolation of the IXR1 gene by map-based cloning revealed that it encodes the AtCESA3 isoform of cellulose synthase. The two known mutant alleles contain point mutations that replace glycine 998 with aspartic acid, and threonine 942 with isoleucine, respectively. The mutations occur in a highly conserved region of the enzyme near the carboxyl terminus that is well separated from the proposed active site. Although the IXR1 gene is expressed in the same cells as the structurally related RSW1 (AtCESA1) cellulose synthase gene, these two CESA genes are not functionally redundant.
在许多高等植物中，异恶草酮和噻唑烷二酮类除草剂（如5-叔丁基-氨甲酰氧基-3-（3-三氟甲基）苯基-4-噻唑烷二酮）会抑制纤维素的合成。拟南芥IXR1和IXR2位点的半显性突变赋予了对异恶草酮和噻唑烷二酮的抗性。通过图位克隆分离出的IXR1基因表明，它编码纤维素合酶的AtCESA3同工型。两个已知的突变等位基因分别包含将甘氨酸998替换为天冬氨酸以及将苏氨酸942替换为异亮氨酸的点突变。这些突变发生在该酶靠近羧基末端的一个高度保守区域，该区域与推测的活性位点相距甚远。尽管IXR1基因与结构相关的RSW1（AtCESA1）纤维素合酶基因在相同细胞中表达，但这两个CESA基因在功能上并非冗余。
