RGL2 controls flower development, ovule number and fertility in Arabidopsis

[EN] DELLA proteins are a group of plant specific GRAS proteins of transcriptional regulators that have a key role in gibberellin (GA) signaling. In Arabidopsis, the DELLA family is formed by five members. The complexity of this gene family raises the question on whether single DELLA proteins have specific or overlapping functions in the control of several GA-dependent developmental processes. To better understand the roles played by RGL2, one of the DELLA proteins in Arabidopsis, two transgenic lines that express fusion proteins of Venus-RGL2 and a dominant version of RGL2, YPet-rgl2A17, were generated by recombineering strategy using a genomic clone that contained the RGL2 gene. The dominant YPet-rg12 Delta 17 protein is not degraded by GAs, and therefore it blocks the RGL2-dependent GA signaling and hence RGL2-dependent development. The RGL2 role in seed germination was further confirmed using these genetic tools, while new functions of RGL2 in plant development were uncovered. RGL2 has a clear function in the regulation of flower development, particularly stamen growth and anther dehiscence, which has a great impact in fertility. Moreover, the increased ovule number in the YPet-rg12 Delta 17 line points out the role of RGL2 in the determination of ovule number.We wish to thank Ms. J. Yun,M.A. Argomániz for technical assistance, and the IBMCP microscopy facility. Edit Syndicate (http://www.editsyndicate.com/) provided proofreading of the manuscript. This work was supported by grants from the Spanish Ministry of Economy and Competitiveness-FEDER [BI02011-26302 and BI02014-55946] and Generalitat Valenciana [ACOMP/2013/048 and ACOMP/2014/106] to M.A.P-A. and National Science Foundation [MCB-0923727] to J.M.A. MAP-A. received a fellowship of the 'Salvador de Madariaga' program from Spanish Ministry of Science and Innovation.Gómez Jiménez, MD.; Fuster Almunia, C.; Ocaña-Cuesta, J.; Alonso, J.; Perez Amador, MA. (2019). RGL2 controls flower development, ovule number and fertility in Arabidopsis. Plant Science. 281:82-92. https://doi.org/10.1016/j.plantsci.2019.01.014S829228

Gibberellin-mediated RGA-LIKE1 degradation regulates embryo sac development in Arabidopsis

[EN] Ovule development is essential for plant survival, as it allows correct embryo and seed development upon fertilization. The female gametophyte is formed in the central area of the nucellus during ovule development, in a complex developmental programme that involves key regulatory genes and the plant hormones auxins and brassinosteroids. Here we provide novel evidence of the role of gibberellins (GAs) in the control of megagametogenesis and embryo sac development, via the GA-dependent degradation of RGA-LIKE1 (RGL1) in the ovule primordia. YPet-rgl1.17 plants, which express a dominant version of RGL1, showed reduced fertility, mainly due to altered embryo sac formation that varied from partial to total ablation. YPet-rgl1.17 ovules followed normal development of the megaspore mother cell, meiosis, and formation of the functional megaspore, but YPet-rgl1.17 plants had impaired mitotic divisions of the functional megaspore. This phenotype is RGL1-specific, as it is not observed in any other dominant mutants of the DELLA proteins. Expression analysis of YPet-rgl1.17 coupled to in situ localization of bioactive GAs in ovule primordia led us to propose a mechanism of GA-mediated RGL1 degradation that allows proper embryo sac development. Taken together, our data unravel a novel specific role of GAs in the control of female gametophyte development.We wish to thank the IBMCP microscopy facility, and Ms J. Yun for technical assistance. We also thank Jennifer Nemhauser (University of Washington, USA) for the HACR sensor. Cambridge proofreading (https://proofreading.org/order/) provided proofreading and editing of this manuscript. This work was supported by grants from the Spanish Ministry for Science and Innovation-FEDER [BIO2017-83138R] to MAP-A and National Science Foundation [MCB-0923727] to JMA. 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