The calcium signaling module CaM–IQM destabilizes IAA–ARF interaction to regulate callus and lateral root formation

Abstract

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. However, whether other signals are involved in governing callus formation, and thus plant regeneration capability, remains largely unclear. Here, we report that the Arabidopsis calcium (Ca 2+ ) signaling module CALMODULIN IQ-MOTIF CONTAINING PROTEIN (CaM–IQM) interacts with auxin signaling to regulate callus and lateral root formation. 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 Ca 2+ -dependent manner. 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. These findings not only define a critical role of CaM–IQM-mediated Ca 2+ signaling in callus and lateral root formation, but also provide insight into the interplay of Ca 2+ signaling and auxin actions during plant regeneration and development.

WOX11: the founder of plant organ regeneration

“…Then WOX11, together with auxin, activates LBD16 and WOX5 / 7 expression during the division of callus founder cells to form the callus primordium (Hu and Xu 2016 ; Liu et al 2018a , Liu et al 2014b ; Sheng et al 2017 ). LBD16 could alternatively be activated by the lateral rooting pathway involving the calcium (Ca 2+ ) signaling module CALMODULIN IQ-MOTIF CONTAINING PROTEIN (CaM–IQM), INDOLE-3-ACETIC ACID INDUCIBLE14 ( IAA14 ) and 19 , and ARF7 and 19 (Fan et al 2012 ; Shang et al 2016 ; Zhang et al 2022 ). Besides LBD16 and WOX5 / 7 , many root stem cell-related genes are also highly induced during the formation of the callus primordium, including PLETHORA1 and 2 ( PLT1 / 2 ) and SCARECROW ( SCR ) (Fan et al 2012 ; Gordon et al 2007 ; Hu et al 2017 ; Kareem et al 2015 ; Kim et al 2018 ; Liu et al 2018a , Liu et al 2014b ; Sugimoto et al 2010 ; Zhai and Xu 2021 ).…”

The long intergenic noncoding RNA ARES modulates root architecture in Arabidopsis

“…Interestingly, isoform and splicing variation analyses revealed a change in isoforms and alternative 3′ ends for known root‐related genes upon ARES downregulation, including PIP5K , HPA1 , and HSP20‐like , respectively (Table S3). To further explore the role of ARES during lateral root development, we investigated the lateral root gene regulatory network (GRN) defined by Lavenus et al 18 Among the 172 genes included in these GRN, 13 were deregulated in the RNAi‐ ARES 6.2 line: 6 were downregulated in RNAi‐ ARES , and 7 upregulated (Figure 3b), notably including well‐known factors participating in lateral root development, like YUCCA5 , 19 IAA19 20 and SHY2/IAA3 , 21 among others. Changes in transcript abundance were confirmed for seven out of eight of these genes in the three RNAi lines, supporting that ARES may play a regulatory role in the expression of these root‐related genes (Figure S5).…”

Genome-Wide Identification and Expression Analysis of the Aux/IAA Gene Family of the Drumstick Tree (Moringa oleifera Lam.) Reveals Regulatory Effects on Shoot Regeneration

“…ARF7 activates SAUR19 expression by binding its promoter directly, and several SAUR genes have been found to exhibit highly increased expression across the coffee somatic embryogenesis process [ 48 ]. There are studies revealing that Auxin-induced callus formation is retarded when the repressive interaction of IAA19 with ARF7 is destabilized [ 49 ]. IAA12 overexpression hampered shoot regeneration capacity, which can be complemented by ARF4 overexpression, and ARF4 regulates shoot regeneration by collaborating with ARF5 and IAA12 [ 21 ].…”