Underlying mechanisms of diversity in tomato fruit morphology

VAN DER KNAAP, ESTHER; RODRÍGUEZ, GUSTAVO RUBÉN; XIAO, HAN

Merida, Mexico

Congreso; Plant Biology 2008; 2008

American Society of Plant Biologist

The domestication of tomato (Solanum lycopersicum) for its fruit characters resulted in a large collection of varieties that differ in fruit morphology. Over the past few years, the underlying molecular basis for some of the diversity has been unraveled. The knowledge of genes that control morphology permits insights into processes that regulate fruit shape and patterning while it also illuminates how domestication shaped tomato fruit. To date, we know of three genes that control tomato fruit morphology. One gene, FW2.2 controls fruit mass whereas the other two genes, OVATE and SUN control fruit shape. We recently cloned SUN and found that the locus arose via an unusual mutation, underscoring the many different ways by which genome evolution and phenotypic changes occur (1). SUN controls elongated fruit shape by increasing fruit length and reducing fruit width, and its effect is most strongly exhibited after fertilization. The effect of SUN on fruit morphology is to increase the oval shape of the seed part of the fruit. The gene encodes a member of the IQ domain family of proteins which have been hypothesized to regulate hormone and/or secondary metabolism levels (1). OVATE also controls elongated fruit shape. Contrary to SUN, OVATE exhibits its most dramatic effect on fruit shape prior to fertilization. The largest effect of OVATE is on the eccentric positioning of the seed in the fruit. OVATE encodes a member of the Ovate Family Proteins (OFP) that acts as a repressor of transcription (2) and interacts with KNOX and BELL type homeodomain proteins (3) in Arabidopsis. FW2.2 controls fruit weight and the encoded protein has been shown to interact with regulators of the cell cycle (4) in tomato. Most of the variation present in the cultivated tomato germplasm is attributed to either SUN or OVATE in accessions carrying elongated fruit whereas FW2.2 appears be fixed. Funded by NSF DBI 0227541. 1. Xiao et al, 2008. Science 319: 1527. 2. Wang et al, 2007. Plant J 50: 858. 3. Hackbusch et al, 2006. PNAS 102: 4908. 4. Cong and Tanksley 2006. Plant Mol Biol 62: 867