Format: ORAL

Gustavo Rodriguez-Alonso1,2, Kenia A. Galvn Alcaraz1, J. Pablo Villa Nuez1, Ramss U. Albarrn Hernndez1, Sofia Esteban Hernndez1,2, Julieta Olvera Berruecos1,2, Selene Napsucialy-Mendivil1, Joseph G. Dubrovsky1, Svetlana Shishkova1*

1 Departamento de Biología Molecular de Plantas, Instituto de Biotecnología - Universidad Nacional Autónoma de México, Cuernavaca, México 2 Centro de Investigación en Dinámica Molecular, Instituto de Investigaciones en Ciencias Básicas y Aplicadas - Universidad Autónoma del Estado de Morelos. Cuernavaca, Morelos, México

To thrive in deserts, Cactaceae plants possess numerous developmental adaptations. Determinate root growth, i.e. the root apical meristem (RAM) consumption, or exhaustion, and subsequent differentiation of all root-apex cells soon after germination, is one of these adaptations (Dubrovsky, 1997). Determinate growth of primary and lateral roots of seedlings of many Cactaceae species from the Cactoideae subfamily (Shishkova et al., 2013) leads to the formation of a compact root system that might provide seedlings with an advantage for survival in arid and semiarid environments. We analyzed the primary-root growth pattern, determinate or indeterminate, for ca. 150 Cactoideae species and most species exhibited determinate growth. Notably, a few species that exhibit indeterminate primary root growth belong to the sole epiphytic tribe, Hylocereeae. In contrast, both Maihuenia species and few analysed Pereskia (and Leuenbergeria) species exhibit indeterminate primary root growth, while this character could be variable between and within Opuntioideae species. To explore the genetic regulation of the RAM exhaustion in Cactaceae, we performed RNA-seq of the primary-root apex of Pachycereus pringlei (Rodriguez-Alonso et al., 2018) and Carnegiea gigantea (this work) on the developmental stages with active and exhausted RAM; and inferred a genetic regulatory network that operate in the root apex. The putative orthologs of the most important regulators of the RAM maintenance reported for Arabidopsis thaliana were also expressed in the root apex of the mentioned cacti species. These transcriptomes, as well as the improved C. gigantea genome (Copetti et al., 2023) and highly fragmented draft genomes of five more Cactoideae species (Copetti et al., 2017, Zhen et al., 2021) allowed us to start the exploration in Cactaceae of the PLT and WOX5 pathways of RAM maintenance described in Arabidopsis thaliana.  Acknowledgements: This work was partially funded by PAPIIT-UNAM IN210221, IN208824 and CONACyT-CF304301.