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A component of the transcription machinery revealed as a new player in tomato pollen and anther development

Researchers from the MOLECULAR BASES OF PLANT DEVELOPMENTAL PHASE TRANSITIONS group at CBGP have collaborated in the characterization of a tomato mutant, pollen deficient1 (pod1), that displays abnormal anther development and lack of viable pollen formation, which led to the production of parthenocarpic fruits.

Pollination is a key development process in the life cycle of flowering plants, which not only makes possible fertilization and seed formation but also determines fruit quality and yield in crop species. Pollen development and maturation comprises multiple cellular changes mediated by a precisely orchestrated gene expression regulation. Significant progress in understanding the genetic and molecular basis of pollen development has been made from the study of mutants in the model species
Arabidopsis thaliana. In tomato, pollen development and the predetermined tapetum degeneration processes are quite similar to that of Arabidopsis; however, only a small number of pollen development related genes have been identified so far.

Genetic and molecular characterization of tomato
pod1 mutant has revealed that this gene encodes the subunit 18 of Mediator multi-protein complex, involved in the RNA polymerase II transcription. The loss of SlMED18 function delayed tapetum degeneration, which resulted in deficient microspore development and scarce production of viable pollen. Expression of pollen marker genes indicated that SlMED18 is essential for the proper transcription of a subset of genes specifically required for pollen formation and fruit development, revealing a key role of SlMED18 in the genetic control of male gametogenesis in tomato. Additionally, SlMED18 is able to rescue developmental abnormalities of the Arabidopsis med18 mutant indicating that most biological functions have been conserved in both species.

The unveiled function of
POD1 gene in ensuring proper gene regulation during pollen ontogeny may contribute to the exploitation of male sterility for heterosis breeding in tomato.

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Original Paper:

Pérez-Martín, F; Yuste-Lisbona, FJ; Pineda, B; García-Sogo, B; del Olmo, I; Alché, JdD; Egea, I; Flores, FB; Piñeiro, M; Jarillo, JA; Angosto, T; Capel, J; Moreno, V; Lozano, R. "Developmental role of the tomato Mediator complex subunit MED18 in pollen ontogeny". Plant Journal. DOI: 10.1111/tpj.14031".

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