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Improving yield by increasing the size of produce is an important selection criterion during the domestication of fruit and vegetable crops. Genes controlling meristem organization and organ formation work in concert to regulate the size of reproductive organs. In tomato, lc and fas control locule number, which often leads to enlarged fruits compared to the wild progenitors. LC is encoded by the tomato ortholog of WUSCHEL ( WUS ), whereas FAS is encoded by the tomato ortholog of CLAVATA 3 ( CLV 3). The critical role of the WUS ‐ CLV 3 feedback loop in meristem organization has been demonstrated in several plant species. We show that mutant alleles for both loci in tomato led to an expansion of the Sl WUS expression domain in young floral buds 2–3 days after initiation. Single and double mutant alleles of lc and fas maintain higher Sl WUS expression during the development of the carpel primordia in the floral bud. This augmentation and altered spatial expression of Sl WUS provided a mechanistic basis for the formation of multilocular and large fruits. Our results indicated that lc and fas are gain‐of‐function and partially loss‐of‐function alleles, respectively, while both mutations positively affect the size of tomato floral meristems. In addition, expression profiling showed that lc and fas affected the expression of several genes in biological processes including those involved in meristem/flower development, patterning, microtubule binding activity, and sterol biosynthesis. Several differentially expressed genes co‐expressed with Sl WUS have been identified, and they are enriched for functions in meristem regulation. Our results provide new insights into the transcriptional regulation of genes that modulate meristem maintenance and floral organ determinacy in tomato.

;Glycosyltransferases are enzymes that catalyze the attachment of a sugar molecule to specific acceptor molecules. These enzymes have been shown to play important roles in a number of biological processes. Whereas a large number of putative glycosyltransferase genes have been identified by genomic sequencing, the functions of most of these genes are unknown. Here we report the characterization of an Arabidopsis mutant, designated gaolaozhuangren1 (glz1), which is allelic to parvus characterized recently. The glz1 mutant exhibited a reduced plant stature, reduced size of organs in the shoot and dark-green leaves, indicating an important role of GLZ1 gene in normal development. The earliest GLZ1 expression appears at the shoot apical region of 4-d-old seedlings, which coincides with the onset of the glz1 morphological phenotypes. GLZ1 is expressed in a tissue-specific and developmentally regulated manner, predominantly in the stem and silique, and moderately in the flower. GLZ1 expression is strong in the midrib of rosette and cauline leaves; however, its expression was not detectable in the midrib of the cotyledon. Further analyses revealed that carbohydrate composition and distribution were aberrant in the glz1 mutant. These, together with the GLZ1 expression pattern, suggest a requirement for the GLZ1 function in normal sink-source transition during plant development.

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