背景回顾：Induction of a pluripotent cell mass, called callus, from detached organs is an initial step in in vitro plant regeneration, during which phytohormone auxin-induced ectopic activation of a root developmental program has been shown to be required for subsequent de novo regeneration of shoots and roots. 

提出问题：However, whether other signals are involved in governing callus formation, and thus plant regeneration capability, remains largely unclear.  

主要发现：Here, we report that the Arabidopsis calcium (Ca2+) signaling module CALMODULIN IQ-MOTIF CONTAINING PROTEIN (CaM–IQM) interacts with auxin signaling to regulate callus and lateral root formation. 

结果1-CaM-IQM与IAA互作：We show that disruption of IQMs or CaMs retards auxin-induced callus and lateral root formation by dampening auxin responsiveness, and that CaM–IQM complexes physically interact with the auxin signaling repressors INDOLE-3-ACETIC ACID INDUCIBLE (IAA) proteins in a Ca2+-dependent manner. 

结果2-CaM6解除IAA19对ARF7的抑制：We further provide evidence that the physical interaction of CaM6 with IAA19 destabilizes the repressive interaction of IAA19 with AUXIN RESPONSE FACTOR 7 (ARF7), and thus regulates auxin-induced callus formation. 

结论：These findings not only define a critical role of CaM–IQM-mediated Ca2+ signaling in callus and lateral root formation, but also provide insight into the interplay of Ca2+ signaling and auxin actions during plant regeneration and development.

 摘 要 

从离体器官中诱导出多能干细胞团，即愈伤组织，是体外植株再生的初始步骤。在此过程中，植物激素生长素诱导的根系发育进程的异位激活被证明是随后的芽和根再生所必需的。然而，目前仍不清楚是否有其他信号参与调控愈伤组织的形成，从而影响植株的再生能力。本文中，作者报道了拟南芥钙离子信号模块CaM–IQM与生长素信号相互作用，调节愈伤和侧根的形成。作者发现，IQM或CaM的扰乱会通过抑制生长素响应，延缓生长素诱导的愈伤和侧根形成，并且CaM-IQM复合物以钙离子依赖的方式与生长素信号转导抑制子IAA蛋白发生物理互作。进一步研究结果显示，CaM6与IAA19的物理互作破坏了IAA19与ARF7的互作，从而解除了IAA19对ARF7的抑制作用，进而调节生长素诱导的愈伤组织形成。本文的研究结果揭示了CaM-IQM介导的钙离子信号在愈伤组织和侧根形成中的关键作用，并且为钙离子信号和生长素互作在植物再生和发育中的作用提供了新的视野。

 胡玉欣