Organelle Ca2+/CAM1-SELTP confers somatic cell embryogenic competence acquisition and transformation in plant regeneration

Abstract

Somatic cell totipotency in plant regeneration represents the forefront of the compelling scientific puzzles and one of the most challenging problems in biology. How somatic embryogenic competence is achieved in regeneration remains elusive. Here, we discover uncharacterized organelle-based embryogenic differentiation processes of intracellular acquisition and intercellular transformation, and demonstrate the underlying regulatory system of somatic embryogenesis-associated lipid transfer protein (SELTP) and its interactor calmodulin1 (CAM1) in cotton as the pioneer crop for biotechnology application. The synergistic CAM1 and SELTP exhibit consistent dynamical amyloplast-plasmodesmata (PD) localization patterns but show opposite functional effects. CAM1 inhibits the effect of SELTP to regulate embryogenic differentiation for plant regeneration. It is noteworthy that callus grafting assay reflects intercellular trafficking of CAM1 through PD for embryogenic transformation. This work originally provides insight into the mechanisms responsible for embryogenic competence acquisition and transformation mediated by the Ca²⁺/CAM1-SELTP regulatory pathway, suggesting a principle for plant regeneration and cell/genetic engineering.

Keywords: Ca2+/CAM1–SELTP interaction; Gossypium hirsutum L.; amyloplast–plasmodesmata organelle; intracellular activation and intercellular transformation; plant regeneration; somatic cell totipotency.