生物形状多样性通常表现在器官对称性的调节和重复形状元素的模式化加工的修饰。1,2,3,4,5是否以及如何协调调节形状确定的这两个方面尚不清楚。5,6,7植物叶片提供了一个有吸引力的系统来研究这个问题,因为它们通常沿着叶片的近端(PD)轴显示出不对称性,它们还可以产生重复的边缘生长,如锯齿或叶状。1叶片形状多样性的一个方面是异形生长,其中单个基因型的叶子形式用渐进的植物年龄进行修饰。8,9,10,11在拟南芥中,有简单叶子的植物,SQUAMOSA启动子结合蛋白样9(SPL9)通过激活CyclinD3表达来控制异源细胞,从而维持成年叶子的增殖生长和延迟分化.12,13然而,SPL9作用对叶片对称性和边缘图案的确切意义尚不清楚。通过结合遗传学,定量形状分析,和延时成像,我们表明,拟南芥叶片的PD对称性随着年龄依赖性SPL9表达梯度而降低,SPL9作用协调调节边缘锯齿的分布和形状以及整体叶片形式。使用比较分析,我们证明了在卡丹明hirsuta中的异源生长重编程,拟南芥的一个复杂的亲戚,还涉及延长细胞增殖的持续时间和延迟分化。我们进一步提供证据表明,SPL9能够促进叶片复杂性的同源异型盒基因的物种特异性作用。总之,我们确定了器官PD生长调节的年龄依赖性层,该层调节了叶片对称性并使叶片形状多样化。
Biological shape diversity is often manifested in modulation of organ symmetry and modification of the patterned elaboration of repeated shape elements.1,2,3,4,5 Whether and how these two aspects of shape determination are coordinately regulated is unclear.5,6,7 Plant leaves provide an attractive system to investigate this problem, because they often show asymmetries along the proximodistal (PD) axis of their blades, along which they can also produce repeated marginal outgrowths such as serrations or leaflets.1 One aspect of leaf shape diversity is heteroblasty, where the leaf form in a single genotype is modified with progressive plant age.8,9,10,11 In Arabidopsis thaliana, a plant with simple leaves, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 9 (SPL9) controls heteroblasty by activating CyclinD3 expression, thereby sustaining proliferative growth and retarding differentiation in adult leaves.12,13 However, the precise significance of SPL9 action for leaf symmetry and marginal patterning is unknown. By combining genetics, quantitative shape analyses, and time-lapse imaging, we show that PD symmetry of the leaf blade in A. thaliana decreases in response to an age-dependent SPL9 expression gradient, and that SPL9 action coordinately regulates the distribution and shape of marginal serrations and overall leaf form. Using comparative analyses, we demonstrate that heteroblastic growth reprogramming in Cardamine hirsuta, a complex-leafed relative of A. thaliana, also involves prolonging the duration of cell proliferation and delaying differentiation. We further provide evidence that SPL9 enables species-specific action of homeobox genes that promote leaf complexity. In conclusion, we identified an age-dependent layer of organ PD growth regulation that modulates leaf symmetry and has enabled leaf shape diversification.