Ori N, Eshed Y, Chuck G, Bowman J L, Hake S
Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA.
Development. 2000 Dec;127(24):5523-32. doi: 10.1242/dev.127.24.5523.
Knotted1-like homeobox (knox) genes are expressed in specific patterns within shoot meristems and play an important role in meristem maintenance. Misexpression of the knox genes, KNAT1 or KNAT2, in Arabidopsis produces a variety of phenotypes, including lobed leaves and ectopic stipules and meristems in the sinus, the region between lobes. We sought to determine the mechanisms that control knox gene expression in the shoot by examining recessive mutants that share phenotypic characteristics with 35S::KNAT1 plants. Double mutants of serrate (se) with either asymmetric1 (as1) or asymmetric2 (as2) showed lobed leaves, ectopic stipules in the sinuses and defects in the timely elongation of sepals, petals and stamens, similar to 35S::KNAT1 plants. Ectopic stipules and in rare cases, ectopic meristems, were detected in the sinuses on plants that were mutant for pickle and either as1 or as2. KNAT1 and KNAT2 were misexpressed in the leaves and flowers of single as1 and as2 mutants and in the sinuses of leaves of the different double mutants, but not in se or pickle single mutants. These results suggest that AS1 and AS2 promote leaf differentiation through repression of knox expression in leaves, and that SE and PKL globally restrict the competence to respond to genes that promote morphogenesis.
类Knotted1同源异型框（knox）基因在茎尖分生组织中以特定模式表达，并在分生组织维持中发挥重要作用。在拟南芥中，knox基因KNAT1或KNAT2的错误表达会产生多种表型，包括叶片裂叶、叶腋（裂片之间的区域）异位托叶和分生组织。我们试图通过研究与35S::KNAT1植物具有相同表型特征的隐性突变体来确定控制茎中knox基因表达的机制。锯齿状（se）与不对称1（as1）或不对称2（as2）的双突变体表现出裂叶、叶腋异位托叶以及萼片、花瓣和雄蕊及时伸长方面的缺陷，类似于35S::KNAT1植物。在pickle与as1或as2的突变体植株的叶腋中检测到异位托叶，在极少数情况下还检测到异位分生组织。在单个as1和as2突变体的叶片和花中以及不同双突变体叶片的叶腋中，KNAT1和KNAT2均有错误表达，但在se或pickle单突变体中则没有。这些结果表明，AS1和AS2通过抑制叶片中的knox表达来促进叶片分化，并且SE和PKL在全局上限制了对促进形态发生的基因作出反应的能力。
