Fruit architecture in polyamine-rich tomato germplasm as influenced by a medley of cell cycle, cell expansion and fruit shape genes

Authors: ANWAR, RAHEEL - University Of Faisalabad; FATIMA, SHAZIA - Purdue University; Mattoo, Autar; HANDA, AVTAR - Purdue University

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2019
Publication Date: 9/29/2019
Citation: Anwar, R., Fatima, S., Mattoo, A.K., Handa, A.K. 2019. Fruit architecture in polyamine-rich tomato germplasm as influenced by a medley of cell cycle, cell expansion and fruit shape genes. Plants. https://doi.org/10.3390/plants8100387.
DOI: https://doi.org/10.3390/plants8100387

Interpretive Summary: Shape of a fruit or vegetable are important to the growers and consumers alike. Although we have some understanding of the genes involved in shaping a fruit, there is little information about the biochemical signals that are essential and contribute to the shape of a commodity including fruits. During our studies involving genetically enhanced tomato, we identified a couple of tomato lines that had an oblong versus round shape. The obovoid shape was distinct from the spherical fruit of wild type control plants. In this manuscript, we demonstrate that a tight link exists between the biogenic molecules (called polyamines) and expression patterns of fruit shape, cell division and cell expansion genes during early fruit development, indicating that polyamines play important roles in tomato fruit architecture. Its contents will be of interest to farmers, fruit growers, biologists, nutritionists, academicians, industry, and scientists.

Technical Abstract: Various genes regulate fruit size and shape, but the biochemical signals regulating these processes during development are not yet known/understood. Transgenic expression of ySpdSyn (yeast Spermidine Synthase) under a constitutive or a fruit-ripening promoter resulted in obovoid from a spherical fruit phenotype of wild type fruit. The obovoid phenotype was evident in as early as 5-day old fruits and continued until the red ripe stage of transgenic fruit. The obovoid phenotype was associated with decreased cell layers and thickness of pericarp. The transgenic floral buds and fertilized ovaries differentially accumulated free and bound forms of polyamines. The bound forms of the polyamines were several-fold higher in transgenic lines compared to isogenic wild-type tissues. Transcript levels of fruit shape genes, SUN1 and OVATE, but not FW2.2 exhibited significant increases 2 days and 5 days after pollination (DAP), which was associated with increases in transcripts levels of CDKB2, CYCB2, KRP1, WEE1. Principal component analysis showed that CYCA2 and CYCD3 clustered with free and bound forms of putrescine, spermidine and spermine. Higher transcript levels of the cell expansion genes CCS52A/B were present in 10 and 20 DAP transgenic fruits, and exhibited negative association with free or bound forms of polyamines. The number of cell layers and thickness of pericarp decreased in the transgenic fruits and was inversely associated with free or bound polyamines in 10 and 20 DAP transgenic ovaries. The polyamine biosynthesis and catabolism genes exhibited generally negative association with bound or free polyamines, except SAMDC2 and transgene ySpdSyn which showed positive association with polyamines. Collectively, these results provide evidence for a tight link between polyamine levels and expression patterns of fruit shape, cell division and cell expansion genes during early fruit development, indicating that polyamines play important roles in tomato fruit architecture.