Characterization of the KNOX class homeobox genes Oskn2 and Oskn3 identified in a collection of cDNA libraries covering the early stages of rice embryogenesis

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A. Dorien Postma-Haarsma, Ira I.G.S. Verwoert, Oscar P. Stronk, Jan Koster, Gerda E.M. Lamers, J. Harry C. Hoge, Annemarie H. Meijer
Plant Molecular Biology, 1999, 39(2): 257-271     追溯原文......本站官方QQ群:62473826
developmental regulation; ectopic expression; embryogenesis; in situ hybridization; KNOX class homeobox genes; rice

For identification of genes involved in embryogenesis in the model cereal rice, we have constructed a collection of cDNA libraries of well-defined stages of embryo development before, during and after organ differentiation. Here, we focus on the possible role of KNOX (maize Knotted1-like) class homeobox genes in regulation of rice embryogenesis. Three types of KNOX clones were identified in libraries of early zygotic embryos. Two of these, Oskn2 and Oskn3, encode newly described KNOX genes, whereas the third (Oskn1) corresponds to the previously described OSH1 gene. In situ hybridizations showed that during the early stages of embryo development, all three KNOX genes are expressed in the region where the shoot apical meristem (SAM) is organizing, suggesting that these genes are involved in regulating SAM formation. Whereas OSH1 was previously proposed to function also in SAM maintenance, Oskn3 may be involved in patterning organ positions, as its expression was found to mark the boundaries of different embryonic organs following SAM formation. The expression pattern of Oskn2 suggested an additional role in scutellum and epiblast development. Transgenic expression of Oskn2 and Oskn3 in tobacco further supported their involvement in cell fate determination, like previously reported for Knotted1 and OSH1 ectopic expression. Whereas Oskn3 transformants showed the most pronounced phenotypic effects during vegetative development, Oskn2 transformants showed relatively mild alterations in the vegetative phase but a more severly affected flower morphology. The observation that the KNOX genes produce similar though distinct phenotypic reponses in tobacco, indicates that their gene products act on overlapping but different sets of target genes, or that cell-type specific factors determine their precise action.

KNOX类同源异盒基因Oskn2和OsKn3在覆盖整个水稻胚胎发生早期的cDNA收集库中的识别与鉴定

为了鉴定模式谷类作物水稻在胚胎发生时期涉及到基因。我们构建了处于器官分化的前中后的胚胎发育明确阶段的各cDNA文库。本文,我们关注KNOX(玉米种knotted1类似突变体)同源异型基因在调控水稻胚胎发生中的可能作用。我在早期的合子胚胎文库中鉴定出三种类型的KNOX基因,其中2个是Oskn2和OsKn3,编码新的KNOX基因,而OsKN1正是以前报道的OSH1基因,原位杂交表明,在胚胎发育的早期阶段,所用三个KNOX基因在SAM(茎端分生组织)组构的区域表达。表明三个KNOX基因都参与调节SAM的形成。而之前有人报道OSH1参与SAM的维持功能。OsKn3可能参与器官定位模式的塑造。它的表达可以区分伴随SMA形成的不同胚器官的边界。Oskn2表达模式表明该基因在盾片和外胚层的发育起作用。Oskn2与OsKn3在烟草中表达进一步支持了KNOX参与了细胞命运决定。如同Knotted1与OSH1的异位表达。Oskn3转化体在营养发育阶段有最显著的表型影响。OsKn2转化体在营养阶段有相对的小的改变。而对花的形态影响较严重。观察发现,KNOX转基因产生与烟草类似的表型。这暗示了这些基因产物功能相互有重叠。但不同的靶基因或那些细胞型的特殊因子决定了它们KNOX基因更精确的行为。


基因列表
  矮秆基因;水稻同源异型盒基因 d6; OSH15;Oskn3
  同源异型盒基因 OSH1; Oskn1
  同源异型盒基因 OSH71; Oskn2