Bruno Leonardo, Pacenza Marianna, Forgione Ivano, Lamerton Liam R, Greco Maria, Chiappetta Adriana, Bitonti Maria B
Dipartimento di Biologia, Ecologia e Scienze della Terra, Università della CalabriaArcavacata di Rende, Italy.
School of Biosciences, University of CardiffCardiff, United Kingdom.
Front Plant Sci. 2017 Jul 27;8:1323. doi: 10.3389/fpls.2017.01323. eCollection 2017.
Cadmium is one of the most widespread pollutant in both terrestrial and marine environment, and its inhibitory effect on plant growth has been largely demonstrated. However, the molecular mechanisms underlying Cd toxicity in plant and mainly in root, as the first organ sensing soil heavy metals, need to be better investigated. To this aim, in the present work we analyzed the growth and the organization of primary root in seedlings exposed to Cd (25 and 50 μM) for 8 days starting from germination. Root length, root meristem size, and organization were evaluated together with the behavior of some of the major molecular players in root growth and patterning. In particular, by using different GFP transgenic lines, we monitored: (i) the expression pattern of WOX5 and SCR transcription factors involved in the establishment and maintenance of stem cell niche and in the control of meristem size; (ii) the expression pattern of the IAA-inducible reporter, PIN 1, 2, 3, 7 auxin carriers and cytokinin-sensitive sensor as relevant components of hormone circuit controlling root growth. We report that Cd exposure inhibits primary root growth via affecting RAM stem cell niche and root radial pattern. At the molecular level, an impairment of auxin maximum accumulation at the root tip, related to a down-regulation and mislocalisation of PIN proteins, and an enhancement of cytokinin-sensitive sensor signal is also detected under Cd treatment, thus suggesting an alteration in the homeostasis of auxin/cytokinin signaling. Moreover, and for the first time Cd toxicity on root growth and pattern has been related to a misexpression of SCR transcription factors which is known to interplay with auxin/cytokinin cross-talk in the control of RAM maintenance and activity.
镉是陆地和海洋环境中分布最广泛的污染物之一，其对植物生长的抑制作用已得到充分证实。然而，植物尤其是作为感知土壤重金属的第一器官——根中，镉毒性的分子机制仍需深入研究。为此，在本研究中，我们分析了从萌发开始暴露于镉（25和50μM）8天的幼苗主根的生长和组织结构。评估了根长、根分生组织大小和组织结构，以及一些参与根生长和模式形成的主要分子参与者的行为。特别是，通过使用不同的绿色荧光蛋白转基因系，我们监测了：（i）参与干细胞龛的建立和维持以及分生组织大小控制的WOX5和SCR转录因子的表达模式；（ii）作为控制根生长的激素回路相关组成部分的IAA诱导型报告基因、PIN 1、2、3、7生长素载体和细胞分裂素敏感传感器的表达模式。我们报告，镉暴露通过影响根顶端分生组织干细胞龛和根径向模式来抑制主根生长。在分子水平上，在镉处理下还检测到根尖生长素最大积累的受损，这与PIN蛋白的下调和定位错误有关，以及细胞分裂素敏感传感器信号的增强，从而表明生长素/细胞分裂素信号稳态的改变。此外，镉对根生长和模式的毒性首次与SCR转录因子的错误表达有关，已知该转录因子在控制根顶端分生组织的维持和活性中与生长素/细胞分裂素相互作用。
