Characterization of the Narrow Sheath Duplicate Factor Pair: Pattern Forming Loci Involved in Maize Leaf Development

为了确定玉米叶片中是否存在发育隔室，提出了遗传学和分子生物学的研究。以前，细胞系分析和玉米分生组织的KNOX（叶片/非叶片身份标记）免疫定位表明，窄鞘突变植物的叶片创建细胞没有利用边缘结构域。成熟时，窄鞘突变体叶片非常狭窄，缺乏通常在玉米叶片边缘发现的特定细胞和组织类型。综上所述，这些数据表明玉米叶片中存在一个边缘结构域，并且这个植物区室可能在分生组织创始细胞阶段通过狭窄鞘1和狭窄鞘2重复基因的活性建立起来。提出了三个项目来测试叶缘的发育是通过创始细胞的细分进入不同的发育域进行的，还是叶缘以一种非分区的方式在很晚的时候形成的。1)克隆镶嵌分析将用于推断Ns2基因功能的发育时间和组织层特异性。该分析还将确定NS2活性是否局限于叶片边缘结构域，还是在其他叶片区域也需要。2)对每个窄鞘基因对应的完整基因组和cDNA克隆进行分离和测序。序列分析将揭示ns1和ns2在结构上的同源程度，并可能提示它们的分子功能。3) Northern分析、RNA原位杂交和免疫组织定位分析在整个叶片发育过程中对Ns基因表达的分析将验证玉米叶片边缘在创始细胞发育阶段由Ns基因的结构域特异性表达形成图案的假设。

Genetic and molecular-biological investigations are proposed in order to determine whether a developmental compartment exists in the maize leaf. Previously, cell-lineage analyses and KNOX (markers of leaf/nonleaf identity) immunolocalizations of maize meristems indicated that a margin domain is not utilized in the leaf founder-cells of narrow sheath mutant plants. At maturity, narrow sheath mutant leaves are extremely narrow and devoid of specific cell and tissue types normally found at the edges of maize leaves. Together, these data indicate that a margin domain exists in the maize leaf and that this plant compartment may be established at the meristematic founder-cell stage via the activity of the duplicate genes narrow sheath1 and narrow sheath2. Three projects are proposed to test whether leaf margin development proceeds via the subdivision of founder-cells into distinct developmental domains or if the leaf margin is patterned much later in a non-compartmentalized manner.1) Clonal mosaic analysis will be used to infer the developmental timing and tissue-layer specificity of Ns2 gene function. This analysis will also determine if NS2 activity is confined to the margin domain of the leaf or is required in other leaf regions.2) Complete genomic and cDNA clones corresponding to each of the narrow sheath genes will be isolated and sequenced. Sequence analyses will reveal the degree of structural homology among nsl and ns2, and may suggest their molecular function.3) Northern analyses, RNA in situ hybridizations and immunohistolocalization assays of Ns gene expression throughout leaf development will test the hypothesis that the margins of maize leaves are patterned during the founder-cell stage of development by the domain-specific expression of the Ns genes.