Oral Presentation International Plant Molecular Biology Conference 2024

Complementation of gibberellin-deficient mutants in specific root layers highlights a dual role for gibberellins in rhizobial infection, nodule formation, and root organogenesis (#379)

Karen Velandia 1 , Alejandro Correa-Lozano 1 , James B. Reid 1 , Eloise Foo 1
  1. University of Tasmania,, Sandy Bay, TAS, Australia

Legumes form a unique association with rhizobia to access atmospheric nitrogen. This association involves the formation of root nodules, specialized structures that serve to host the bacteria and to provide the ideal environment for nitrogen fixation and nutrient exchange between plant and rhizobia. Precise coordination of rhizobial infection in the epidermis and nodule formation in the inner root layers is essential for successful symbiosis. Plant hormones play a crucial role in regulating these complex processes, with their spatial and temporal activation dictating nodulation progression. We employed a powerful approach of specific epidermal and endodermal complementation of severely gibberellin-deficient na pea mutants, coupled with the analysis of the cytokinin-responsive promoter TCSn and gene expression dynamics via RNAseq. We demonstrate gibberellins restrict infection in the epidermis, limiting bacterial entry and regulating infection thread progression and branching in the cortex by suppressing cytokinin response. Moreover, gibberellins are essential in the endodermis to promote nodule organogenesis and lateral root development. In contrast, gibberellins presence in the epidermis does not influence nodule or root development. Careful comparison of RNAseq data of epidermal and endodermal complementation allows us to use a unique approach to identify genes potentially involved in the regulation of infection or nodule and root organogenesis. Gibberellins play a crucial role in regulating key checkpoints in nodulation, including infection thread progression into the cortex, nodule primordia colonization, and progression of the nodule development. This knowledge will facilitate the integration of the various roles of plant hormones in nodulation and root development processes.