“生长素极性输送”是植物所有发育过程中的一个因素，但关于这个因素是怎样发挥作用的仍有很多东西需要了解。在细胞中，“生长素定向输送”由PIN蛋白载体复合物控制。现在，研究人员已经开发出一个新的计算模型，来描述根系中细胞内和细胞间的扩散及由PIN帮助进行的生长素输送。该模型涉及植物发育的两大问题。第一，它支持关于生长素在引导根生长方面有一个最大值和一个梯度的概念。第二，它反映了一个分子何以能够产生一系列信息：整个器官生长区的一个浓度梯度与生长素最大值密切相关。另一篇相关的论文表明，４个PLETHORA基因是根发育所必不可少的，是生长素梯度的候选输出因子。
原始出处:
Nature 449, 1053-1057 (25 October 2007) | doi:10.1038/nature06206; Received 5 July 2007; Accepted 30 August 2007
PLETHORA proteins as dose-dependent master regulators of Arabidopsis root development
Carla Galinha1,2,3, Hugo Hofhuis1,2, Marijn Luijten1, Viola Willemsen1, Ikram Blilou1, Renze Heidstra1 & Ben Scheres1
Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
These authors contributed equally to this work.
Present address: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
Correspondence to: Ben Scheres1 Correspondence and requests for materials should be addressed to B.S. (Email: b.scheres@uu.nl).
Factors with a graded distribution can program fields of cells in a dose-dependent manner1, 2, but no evidence has hitherto surfaced for such mechanisms in plants. In the Arabidopsis thaliana root, two PLETHORA (PLT) genes encoding AP2-domain transcription factors have been shown to maintain the activity of stem cells3. Here we show that a clade of four PLT homologues is necessary for root formation. Promoter activity and protein fusions of PLT homologues display gradient distributions with maxima in the stem cell area. PLT activities are largely additive and dosage dependent. High levels of PLT activity promote stem cell identity and maintenance; lower levels promote mitotic activity of stem cell daughters; and further reduction in levels is required for cell differentiation. Our findings indicate that PLT protein dosage is translated into distinct cellular responses.
