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Columnar growth phenotype in apple results from gibberellin deficiency by ectopic expression of a dioxygenase gene.
Tree Physiology ( IF 4 ) Pub Date : 2020-04-25 , DOI: 10.1093/treephys/tpaa049
Kazuma Okada 1 , Masato Wada 1 , Yumiko Takebayashi 2 , Mikiko Kojima 2 , Hitoshi Sakakibara 2, 3 , Masaru Nakayasu 4 , Masaharu Mizutani 4 , Masatoshi Nakajima 5 , Shigeki Moriya 1 , Taku Shimizu 1 , Kazuyuki Abe 1
Affiliation  

The apple cultivar McIntosh Wijcik, which is a mutant of ‘McIntosh’, exhibits a columnar growth phenotype (short internodes, few lateral branches, many spurs, etc.) that is controlled by a dominant Co gene. The candidate gene (MdDOX-Co), encoding a 2-oxoglutarate-dependent dioxygenase, is located adjacent to an insertion mutation. Non-columnar apples express MdDOX-Co in the roots, whereas columnar apples express MdDOX-Co in the aerial parts as well as in the roots. However, the function of MdDOX-Co remains unknown. Here, we characterized tobacco plants overexpressing MdDOX-Co. The tobacco plants showed the typical dwarf phenotype, which was restored by application of gibberellin A3 (GA3). Moreover, the dwarf tobacco plants had low concentrations of endogenous bioactive gibberellin A1 (GA1) and gibberellin A4 (GA4). Similarly, ‘McIntosh Wijcik’ contained low endogenous GA4 concentration and its dwarf traits (short main shoot and internodes) were partially reversed by GA3 application. These results indicate that MdDOX-Co is associated with bioactive GA deficiency. Interestingly, GA3 application to apple trees also resulted in an increased number of lateral branches and a decrease in flower bud number, indicating that gibberellin (GA) plays important roles in regulating apple tree architecture by affecting both lateral branch formation (vegetative growth) and flower bud formation (reproductive growth). We propose that a deficiency of bioactive GA by ectopic expression of MdDOX-Co in the aerial parts of columnar apples not only induces dwarf phenotypes but also inhibits lateral branch development and promotes flower bud formation, and assembly of these multiple phenotypes constructs the columnar tree form.

中文翻译:

苹果中的柱状生长表型是由赤霉素缺乏通过双加氧酶基因的异位表达引起的。

苹果品种McIntosh Wijcik是“ McIntosh”的突变体,具有柱状生长表型(节间短,侧枝少,马刺等),受显性Co基因控制。编码2-氧戊二酸依赖性双加氧酶的候选基因(MdDOX-Co)与插入突变相邻。非柱状苹果在根部表达MdDOX-Co,而柱状苹果在地上部分和根部表达MdDOX-Co。但是,MdDOX-Co的功能仍然未知。在这里,我们表征了过量表达MdDOX-Co的烟草植物。烟草植株表现出典型的矮表型,通过赤霉素A的施用可以恢复该表型。3(GA 3)。此外,矮烟草植物具有低浓度的内源性生物活性赤霉素A 1(GA 1)和赤霉素A 4(GA 4)。同样,“ McIntosh Wijcik”的内源GA 4浓度低,其矮化性状(主茎短和节间短)被GA 3施用部分逆转。这些结果表明,MdDOX-Co与生物活性GA缺乏有关。有趣的是,GA 3施用到苹果树上还导致侧枝增加,花芽数减少,表明赤霉素(GA)通过影响侧枝的形成(营养生长)和花芽的形成,在调节苹果树的结构中起着重要的作用(生殖生长)。我们提出通过柱状苹果空中异位表达MdDOX-Co缺乏生物活性GA,不仅会诱导矮化表型,而且会抑制侧枝发育并促进花蕾的形成,而这些多种表型的组装会构建柱状树形。
更新日期:2020-04-25
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