RESEARCH

Plants exhibit a remarkable diversity of forms in nature, reflecting variation in the size, shape, and position of their different organs. The number and arrangement of these organs form the basis of plant architecture. Our laboratory is focused on understanding the control of inflorescence architecture, the region of the plant where flowers are formed. We aim to uncover the genetic networks that regulate inflorescence development and how these networks have evolved in different species to generate the vast diversity of architectures observed in nature.

Different Types of Inflorescences

In the classification of inflorescences, one important distinction is between determinate and indeterminate types. Inflorescences in which the apical meristem of the stem has unlimited growth capacity are termed indeterminate. In contrast, inflorescences in which the apical meristem forms a terminal flower are termed determinate. Another key distinction is between simple and compound inflorescences. In simple inflorescences, flowers develop directly from the shoot apical meristem, meaning they form directly on the main inflorescence axis. In contrast, in compound inflorescences, the primary inflorescence axis does not produce the flowers itself but branches to form secondary or higher-order axes where flowers develop.

The position where flowers are formed depends on the identity of the inflorescence meristems—whether the apical meristem remains as an inflorescence meristem or becomes floral, and whether the primary inflorescence meristem gives rise to floral or secondary inflorescence meristems. We study the gene network that confers identity to inflorescence meristems. Our research is mainly divided into two lines of investigation.

FOCUS

Control of Inflorescence Architecture in Arabidopsis

On one hand, we work with the model species *Arabidopsis thaliana*, which has a simple indeterminate inflorescence. The indeterminate growth of the Arabidopsis inflorescence, as well as that of many other species with indeterminate inflorescences, is due to the activity of the *TERMINAL FLOWER1* (*TFL1*) gene, which prevents the inflorescence meristem from becoming floral. To achieve this, *TFL1* is expressed in the inflorescence meristem, thereby repressing the expression of the floral identity genes *LFY* and *AP1* in that region. We study how *TFL1* expression is established in the inflorescence meristem, which genes regulate its expression, and how these genes influence inflorescence architecture.

In situ hybridization showing expression of TFL1 (blue) and LFY (red) in an Arabidopsis inflorescence apex. (Image courtesy of Cristina Ferrándiz) Control of Inflorescence Development in Legume Compound Inflorescences

As a comparative system, we also work with model legume species, such as pea and *Medicago truncatula*, which exhibit indeterminate compound inflorescences where flowers are formed on lateral secondary inflorescences. In the genetic network that specifies meristem identity in legumes, in addition to homologs of *TFL1*, *LFY*, and *AP1*, new genes are also involved, such as *VEG1*, which is responsible for the formation of secondary inflorescences. We are engaged in the identification and characterization of genes that define secondary inflorescence identity and in the analysis of how the meristem identity gene network has evolved in legumes to give rise to compound inflorescences.

Praena-Tamayo Jesús Tamayo, Ilara Gabriela, Frasson Budzinski, Nicolas Delhomme, Thomas Moritz,  Francisco Madueño, Reyes Benlloch (2022) CHARACTERIZATION OF METABOLIC CHANGES ASSOCIATED WITH FLORAL TRANSITION IN ARABIDOPSIS: RAFFINOSE SYNTHASE 5 CONTRIBUTES TO DETERMINE THE TIMING OF FLORAL TRANSITION BioRxiv2022, .04.29.490013;  doi: https://doi.org/10.1101/2022.04.29.490013

Pautot, V.; Berbel, A.; Cayla, T.; Eschstruth, A.; Adroher, B.; Ratet, P.; Madueño, F.; Laufs, P (2022).  Arabidopsis thaliana SHOOT MERISTEMLESS SUBSTITUTES FOR Medicago truncatula SINGLE LEAFLET1 TO FORM COMPLEX LEAVES AND PETALS.  J. Mol. Sci. 2022, 23, 14114. https://doi.org/10.3390/ijms232214114