ERAMOSA controls lateral branching in snapdragon

Abstract

Plant forms display a wide variety of architectures, depending on the number of lateral branches, internode elongation and phyllotaxy. These are in turn determined by the number, the position and the fate of the Axillary Meristems (AMs). Mutants that affect AM determination during the vegetative phase have been isolated in several model plants. Among these genes, the GRAS transcription factor LATERAL SUPPRESSOR (Ls) plays a pivotal role in AM determination during the vegetative phase. Hereby we characterize the phylogenetic orthologue of Ls in Antirrhinum, ERAMOSA (ERA). Our data supported ERA control of AM formation during both the vegetative and the reproductive phase in snapdragon. A phylogenetic analysis combined with an analysis of the synteny of Ls in several species strongly supported the hypothesis that ERA is a phylogenetic orthologue of Ls, although it plays a broader role. During the reproductive phase ERA promotes the establishment of the stem niche at the bract axis but, after the reproductive transition, it is antagonized by the MADS box transcription factor SQUAMOSA (SQUA). Surprisingly double mutant era squa plants display a squa phenotype developing axillary meristems, which can eventually turn into inflorescences or flowers.The aerial plant body derives from the Shoot Apical Meristem (SAM), through the iterative production of phytomers. A phytomer unit is comprised of a node, to which a leaf is anchored, the corresponding internode and an Axillary Meristem (AM) at the leaf axil 1 . AM initiation occurs at the anlagen of the apical meristem, giving rise to new buds, again formed by a set of phytomers that can remain dormant or grow out 2 . Plants produce new AMs throughout their life cycle, but the nature and properties of AMs change during the different developmental phases. This becomes evident after the floral transition, since the committed floral meristems are indeed products of AMs and are homologous to vegetative axillary buds 3 . Two theories have been proposed to explain AM formation. The 'detached meristem' theory proposes that the SAM gives rise to AMs during the production of leaf primordia In several plant species, mutants impaired in plant architecture have been described, suggesting a tight genetic control. They are grouped into three main classes: mutants affected in AM initiation, meristem outgrowth, or both 6 . An interesting mutant altered in AM initiation is the tomato lateral suppressor (ls) 7 . Ls function is quite conserved, as indicated by its orthologues in Arabidopsis thaliana (LAS) and in Oryza sativa (MONOCULM1, MOC1) 7-9 . All these mutants fail to produce vegetative AMs. Compared to wild-type plants, tomato ls plants produce fewer flowers (without petals); similarly the rice moc1 rachis forms fewer branches and spikelets 9 . Conversely, the Arabidopsis las plants do not develop lateral branches during vegetative growth, but inflorescences and flowers appear normal.The Antirrhinum majus eramosa phenotype is caused by the disruption of the Ls orthologue ERA. era pla...

Time-Course Transcriptome Analysis of Arabidopsis Siliques Discloses Genes Essential for Fruit Development and Maturation

“…For RT-qPCR analyses, 0.5-μg samples of total RNA were used for firststrand cDNA synthesis with the ImProm-II Reverse Transcription System, as already described by Mizzotti et al (2017). RT-qPCR profiling was carried out using the iQ SYBR Green Supermix (Bio-Rad) and the Bio-Rad iCycler iQ Optical System (software version 3.0a), with the primers listed in Supplemental Table S13.…”

The Role of Transcription Factors in the Regulation of Plant Shoot Branching

“…For example, it was found that the formation of the AM in Antirrhinum majus requires ERAMOSA ( ERA ), a gene encoding a GRAS transcription factor (orthologous to LAS in Arabidopsis ). The basic role of ERA in AM formation is consistent with that of LAS/MOC1/ERA in preventing cell differentiation in the boundary area and in stimulating AM formation [ 57 ].…”

GRAS transcription factor PINNATE-LIKE PENTAFOLIATA2 controls compound leaf morphogenesis in Medicago truncatula

“…S8 ). No member from the PINNA2 clade has been functionally characterized to date, but its sister LAS clade contains many functionally identified members, including rice ( Oryza sativa ) MOC1 ( Li et al 2003 ), tomato Ls ( Schumacher et al 1999 ), Arabidopsis LAS ( Greb et al 2003 ), snapdragon ( Antirrhinum majus ) ERAMOSA ( Mizzotti et al 2017 ), and strawberry ( Fragaria vesca ) LAM proteins ( Feng et al 2021 ) ( Fig. 4B ).…”