Submitted to: Journal of Experimental Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/21/2010
Publication Date: 10/1/2010
Citation: Pan, I., Giovannoni, J.J., Irisch, V. 2010. Functional diversification of AGAMOUS lineage genes in regulating tomato flower and fruit development. Journal of Experimental Botany. 61:1795-1806. Interpretive Summary: Numerous genome duplication events have occurred in the genomes of the lineages leading to present day flowering plants. MADS box transcription factors have attracted particular interest due to their known roles in a great variety of plant developmental processes and especially flower and fruit development. The duplication and subsequent diversification in function of MADS box genes may have played an important role in the origin and diversification of flowering plant species that currently occupy the planet. In this study, we have carried out loss of function analyses of a pair of duplicated MADS-box genes, TAG1 and TAGL1 using RNA interference. (RNAi) We have found that TAGL1 plays a novel role in regulating tomato fruit ripening and has a qualitatively distinct function from TAG1. As in earlier studies, we found that TAG1 plays roles in tomato in specifying normal stamen and carpel development.
Technical Abstract: MADS box transcription factors have been shown to play critical roles in many aspects flower and fruit development in angiosperms. Tomato possesses two representatives of the AGAMOUS MADS gene lineage, TOMATO AGAMOUS (TAG1) and TOMATO AGAMOUS-LIKE1 (TAGL1), allowing for an analysis of diversification of function upon duplication. Using RNAi silencing, we have produced transgenic tomato lines that downregulate either TAGL1 or TAG1 transcript accumulation. TAGL1 RNAi lines show no defects in stamen and carpel identity, but show defects in fruit ripening. In contrast TAG1 RNAi lines show defects in stamen and carpel development. In addition TAG1 RNAi lines produce red ripe fruit, although they are defective in determinacy and produce ectopic internal fruit structures. We also characterized e2814, an EMS (ethyl methane sulfonate) induced mutation that is temperature sensitive and produces fruit phenotypes similar to that of TAG1 RNAi lines. Both TAG1 and TAGL1 expression are not disrupted in the e2814 mutant, suggesting that the gene corresponding to the e2814 mutant represents a distinct locus that is likely to be functionally downstream of TAG1 and TAGL1. Based on these analyses, we discuss possible modes by which these gene duplicates have diversified and how such changes may be responsible for species specific morphological differences.