Role of the gibberellin receptors GID1 during fruit-set in Arabidopsis

[EN] Gibberellins (GAs) play a critical role in fruit-set and fruit growth. Gibberellin is perceived by its nuclear receptors GA INSENSITIVE DWARF1s (GID1s), which then trigger degradation of downstream repressors DELLAs. To understand the role of the three GA receptor genes (GID1A, GID1B and GID1C) in Arabidopsis during fruit initiation, we have examined their temporal and spatial localization, in combination with analysis of mutant phenotypes. Distinct expression patterns are revealed for each GID1: GID1A is expressed throughout the whole pistil, while GID1B is expressed in ovules, and GID1C is expressed in valves. Functional study of gid1 mutant combinations confirms that GID1A plays a major role during fruit-set and growth, whereas GID1B and GID1C have specific roles in seed development and pod elongation, respectively. Therefore, in ovules, GA perception is mediated by GID1A and GID1B, while GID1A and GID1C are involved in GA perception in valves. To identify tissue-specific interactions between GID1s and DELLAs, we analyzed spatial expression patterns of four DELLA genes that have a role in fruit initiation (GAI, RGA, RGL1 and RGL2). Our data suggest that GID1A can interact with RGA and GAI in all tissues, whereas GID1C-RGL1 and GID1B-RGL2 interactions only occur in valves and ovules, respectively. These results uncover specific functions of each GID1-DELLA in the different GA-dependent processes that occur upon fruit-set. In addition, the distribution of GA receptors in valves along with lack of expression of GA biosynthesis genes in this tissue, strongly suggests transport of GAs from the developing seeds to promote fruit growth.We wish to thank Dr Masatoshi Nakajima (University of Tokyo, Japan) for providing the pGID1:GID1-GUS lines, and Dr Peter Hedden (Rothamsted Research, UK) for the pGA20ox:GA20ox-GUS lines. We also thank Ms C. Fuster and M. A. Argomaniz for technical assistance. This work has been supported by grants BIO2008-01039 and BIO2011-26302 from the Spanish Ministry of Science and Innovation and ACOMP/2010/079 and ACOMP/2011/287 from the Generalitat Valenciana for M. A. P.-A. and USDA grants 2010-65116-20460 and 2014-67013-21548 for T. P. S. C. G.-G. received a JAE PhD fellowship from the Spanish Council for Scientific Research (CSIC).Gallego Giraldo, C.; Hu, J.; Urbez Lagunas, C.; Gómez Jiménez, MD.; Sun, TP.; Perez Amador, MA. (2014). Role of the gibberellin receptors GID1 during fruit-set in Arabidopsis. Plant Journal. 79(6):1020-1032. doi:10.1111/tpj.12603S1020103279

Identification of MeC3HDZ1/MeCNA as a potential regulator of cassava storage root development

[EN] The storage root (SR) of cassava is the main staple food in sub-Saharan Africa, where it feeds over 500 million people. However, little is known about the genetic and molecular regulation underlying its development. Unraveling such regulation would pave the way for biotechnology approaches aimed at enhancing cassava productivity. Anatomical studies indicate that SR development relies on the massive accumulation of xylem parenchyma, a cell-type derived from the vascular cambium. The C3HDZ family of transcription factors regulate cambial cells proliferation and xylem differentiation in Arabidopsis and other species. We thus aimed at identifying C3HDZ proteins in cassava and determining whether any of them shows preferential activity in the SR cambium and/or xylem. Using phylogeny and synteny studies, we identified eight C3HDZ proteins in cassava, namely MeCH3DZ1-8. We observed that MeC3HDZ1 is the MeC3HDZ gene displaying the highest expression in SR and that, within that organ, the gene also shows high expression in cambium and xylem. In-silico analyses revealed the existence of a number of potential C3HDZ targets displaying significant preferential expression in the SR. Subsequent Y1H analyses proved that MeC3HDZ1 can bind canonical C3HDZ binding sites, present in the promoters of these targets. Transactivation assays demonstrated that MeC3HDZ1 can regulate the expression of genes downstream of promoters harboring such binding sites, thereby demonstrating that MeC3HDZ1 has C3HDZ transcription factor activity. We conclude that MeC3HDZ1 may be a key factor for the regulation of storage root development in cassava, holding thus great promise for future biotechnology applications.This work was funded by grants from the Spanish Ministry of Science (PID2019-108084RB-I00 and PID2021-125829OB-I00 to JA and PID2021-1274610B-I00 to JB) . JB is sponsored by a Ramon y Cajal contract (RYC2019-026537-I) .Solé-Gil, A.; López, A.; Ombrosi, D.; Urbez Lagunas, C.; Brumos, J.; Agustí, J. (2024). Identification of MeC3HDZ1/MeCNA as a potential regulator of cassava storage root development. Plant Science. 339. https://doi.org/10.1016/j.plantsci.2023.11193833