Abstract
Tomato is a model species for fleshy fruit development. The shapes and sizes of tomato (Solanum lycopersicum L.) are mainly controlled by several loci, including locule number (lc). Two single nucleotide polymorphisms were found downstream of WUSCHEL (SlWUS) in a putative tomato CArG cis-regulatory element. The lc mutation may affect the binding of AGAMOUS(AG), cause the up-regulation of SlWUS and result in increased locule numbers. In this study, tissue expression levels showed that SlWUS is expressed in young floral buds and shoot apexes. Silencing SlWUS on an lc mutant genetic background with an RNA interference (RNAi) strategy resulted in smaller flowers and fruit than those of the wild-type plants, with decreased locule number. Further study revealed that the SlWUS RNAi lines exhibited altered expression levels of the TAG1 and SlCLV3 genes that participate in the regulation of tomato flower and fruit locule development. In conclusion, this study provides the first genetic evidence that SlWUS may be the candidate gene of the lc locus and reveals the function of SlWUS in flower development.
Highlights
Tomato (Solanum lycopersicum L.) is an ideal model plant for fruit development research (Klee and Giovannoni, 2011; Consortium, 2012)
SlWUS expression was detected in the young flower buds, shoot apexes, and inflorescence meristem/floral meristem (IM/FM); expression was undetectable in the roots, stems, leaves, and fruits
Our results showed that SlWUS was expressed during flower development, which indicates an important function for SlWUS in the development of tomato flowers
Summary
Tomato (Solanum lycopersicum L.) is an ideal model plant for fruit development research (Klee and Giovannoni, 2011; Consortium, 2012). Domesticated tomato fruit is enlarged 1000 times compared to its wild progenitors, which is an extreme case. In this dramatic transition, both carpel cell division and carpel number determine the final size of tomato fruit (Tanksley, 2004). Low expression levels of the large-fruited allele of FW2.2 stimulate cell division, which leads to increases in the final size of tomato fruit. Increased locule number has the greatest effect on tomato fruit size, which is derived from the carpels in tomato flowers. Almost all wild tomatoes and several small-fruited tomato cultivars produce fruits with only two to four locules. Increased locule number contributes as much as 50% variance to fruit enlargement and is believed to represent a late step in the substantial increase in tomato fruit
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