JOINTLESS Maintains Inflorescence Meristem Identity in Tomato

• Published in: Plant and cell physiology Vol. 65; no. 7; pp. 1197 - 1211
• Main Authors: Huerga-Fernández, Samuel, Detry, Nathalie, Orman-Ligeza, Beata, Bouché, Frédéric, Hanikenne, Marc, Périlleux, Claire
• Format: Journal Article Web Resource
• Language: English
• Published: Japan Oxford University Press (OUP) 30.07.2024; Oxford University Press
• Subjects: Abscission; Biologie végétale (sciences végétales, sylviculture, mycologie...); Branching; Flower development; Gene Expression Regulation, Plant; Inflorescence; Inflorescence - genetics; Inflorescence - growth & development; Life sciences; Meristem - genetics; Meristem - growth & development; Mutation; Phenotype; Phytobiology (plant sciences, forestry, mycology...); Plant Proteins - genetics; Plant Proteins - metabolism; Regular Paper; Sciences du vivant; Solanum lycopersicum; Solanum lycopersicum - genetics; Solanum lycopersicum - growth & development; Solanum lycopersicum - metabolism; Tomato; Branching; Flower development; Tomato; Solanum lycopersicum; Inflorescence; Abscission
• ISSN: 0032-0781; 1471-9053; 1471-9053
• DOI: 10.1093/pcp/pcae046

JOINTLESS (J) was isolated in tomato (Solanum lycopersicum) from mutants lacking a flower pedicel abscission zone (AZ) and encodes a MADS-box protein of the SHORT VEGETATIVE PHASE/AGAMOUS-LIKE 24 subfamily. The loss of J function also causes the return to leaf initiation in the inflorescences, indicating a pivotal role in inflorescence meristem identity. Here, we compared jointless (j) mutants in different accessions that exhibit either an indeterminate shoot growth, producing regular sympodial segments, or a determinate shoot growth, due to the reduction of sympodial segments and causal mutation of the SELF-PRUNING (SP) gene. We observed that the inflorescence phenotype of j mutants is stronger in indeterminate (SP) accessions such as Ailsa Craig (AC), than in determinate (sp) ones, such as Heinz (Hz). Moreover, RNA-seq analysis revealed that the return to vegetative fate in j mutants is accompanied by expression of SP, which supports conversion of the inflorescence meristem to sympodial shoot meristem in j inflorescences. Other markers of vegetative meristems such as APETALA2c and branching genes such as BRANCHED 1 (BRC1a/b) were differentially expressed in the inflorescences of j(AC) mutant. We also found in the indeterminate AC accession that J represses homeotic genes of B- and C-classes and that its overexpression causes an oversized leafy calyx phenotype and has a dominant negative effect on AZ formation. A model is therefore proposed where J, by repressing shoot fate and influencing reproductive organ formation, acts as a key determinant of inflorescence meristems.