Williams-Carrier R E, Lie Y S, Hake S, Lemaux P G
Department of Plant and Microbial Biology, University of California, Berkeley 94702-3102, USA.
Development. 1997 Oct;124(19):3737-45. doi: 10.1242/dev.124.19.3737.
The homeobox gene, knotted1, (kn1) is expressed in shoot meristems and is required for maintaining indeterminacy and preventing cellular differentiation. Awns, extensions of the bract-like lemma found in all grass inflorescences, are normally determinate structures. We show that ectopic expression of kn1 in the barley awn is sufficient to direct the development of ectopic meristems, forming inflorescence-like structures. This homeotic transformation is similar to the phenotype produced by misexpression of the barley hvknox3 gene, associated with the dominant Hooded mutant (Müller, K. J., Romano, N., Gerstner, O., Garcia-Maroto, F., Pozzi, C., Salamini, F. and Rohde, W. (1995) Nature 374, 727-730). We suggest that the inverse polarity of the ectopic flowers seen in Hooded and transgenic kn1 plants results from the transformation of the awn into reiterative inflorescence axes. We observed that the protein and mRNA localization of the transgene, driven by a constitutive promoter, is similar to the expression pattern of hvknox3 in awns of Hooded mutants, suggesting posttranscriptional regulation.
同源异型框基因knotted1（kn1）在茎尖分生组织中表达，是维持细胞的 indeterminacy 和防止细胞分化所必需的。芒是所有禾本科植物花序中类似苞片的外稃的延伸部分，通常是 determinate 结构。我们发现，kn1在大麦芒中的异位表达足以引导异位分生组织的发育，形成类似花序的结构。这种同源异型转变类似于大麦hvknox3基因错误表达所产生的表型，该基因与显性 Hooded 突变体有关（Müller, K. J., Romano, N., Gerstner, O., Garcia-Maroto, F., Pozzi, C., Salamini, F. 和 Rohde, W. (1995) Nature 374, 727 - 730）。我们认为，在 Hooded 和转基因 kn1 植物中看到的异位花的反向极性是由于芒转变为重复的花序轴所致。我们观察到，由组成型启动子驱动的转基因的蛋白质和mRNA定位类似于 Hooded 突变体芒中hvknox3的表达模式，表明存在转录后调控。
