Abstract
In Arabidopsis thaliana, JAGGED (JAG) is a transcription inhibitor that controls the development of leaf polarity and regulates the expression of genes controlling lateral organ formation. Liriodendron tulipifera is an ornamental tree with extraordinary tulip-shaped flowers and goose web-like leaves, this is one of the suitable plants for morphological development research. To investigate the potential functions of the LtuJAG gene, we isolated the full-length LtuJAG from L. tulipifera, transferred it into A. thaliana via agrobacterium-mediated transformation, and monitored its expression pattern. Subcellular localization showed that LtuJAG was located in the nucleus. RT-qPCR assays indicated that LtuJAG was expressed mainly in leaf buds and flowers, but not in mature leaves and stems. GUS staining results showed that LtuJAG was expressed in the shoot apical meristem (SAM). Overexpressing LtuJAG changed A. thaliana leaf shapes, causing a moderate serration and a slight asymmetric distribution in the medio-lateral and proximal-distal axes. Ectopic expression of LtuJAG induced the expression of lateral organ boundary suppressors JAGGED LATERAL ORGANS (JLO) and ARABIDOPSIS THALIANA HOMEOBOX1 (ATH1). It also repressed the expression of the apical meristem suppressor class-1 KNOX gene (KNOX I) and altered endogenous hormone levels. Our results suggest that LtuJAG plays a role in negatively regulating leaf polarity formation in L. tulipifera.
Highlights
The organ development of seed plants usually undergoes two opposite modes: (1) root and stem development, which displays overall radial symmetry; (2) development of lateral organs such as leaves and flowers, which show an obvious asymmetry [1]
Our study found that LtuJAG can upregulate the expression of the KNOX I negative regulator, indicating that JAG may indirectly downregulate the expression of KNOX I during the development of lateral meristematic tissue
To study the temporal expression pattern of genes associated with leaf serration, we examined the transcript levels of leaf serration related genes in wild-type A. thaliana leaves at different growth stages and confirmed all genes were expressed at leaf primordia differentiation (10 days after seed germination), and to some extent, some genes were not even expressed at the maturation (25 days after seed germination), reproductive
Summary
The organ development of seed plants usually undergoes two opposite modes: (1) root and stem development, which displays overall radial symmetry; (2) development of lateral organs such as leaves and flowers, which show an obvious asymmetry [1]. Genetic evidence has revealed that leaves underwent four morphological changes during their evolution: curling into a cone, developing short and flexible petioles as well as serrated edges, forming compound pinnate leaves, and stacking with each other along the branches to adjust the phyllotaxis and reduce drag [3]. Due to their morphological plasticity, leaves are ideal research subjects for under-standing organ morphogenesis and environmental adaptability. The development of the leaves includes three processes: leaf initiation, leaf polarity establishment, and leaf morphology modulation [4]. Many genes involved in leaf development have been identified, including KNOX I family genes, 4.0/)
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