Background GROWTH-REGULATING FACTORs (GRFs), a type of plant-specific transcription factors, play important roles in regulating plant growth and development. Although GRF gene family has been identified in various plant species, a genome-wide analysis of this family in lettuce (Lactuca sativa L.) has not been reported yet. Results Here we identified 15 GRF genes in lettuce and performed comprehensive analysis of them, including chromosomal locations, gene structures, and conserved motifs. Through phylogenic analysis, we divided LsaGRFs into six groups. Transactivation assays and subcellular localization of LsaGRF5 showed that this protein is likely to act as a transcriptional factor in the cell nucleus. Furthermore, transgenic lettuce lines overexpressing LsaGRF5 exhibited larger leaves, while smaller leaves were observed in LsaMIR396a overexpression lines, in which LsaGRF5 was down-regulated. Conclusions These results in lettuce provide insight into the molecular mechanism of GRF gene family in regulating leaf growth and development and foundational information for genetic improvement of the lettuce variations specialized in leaf character.

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Background: The plant-specific YABBY transcription factor plays important roles in the development of lateral organs, the establishment of adaxial-abaxial polarity and abiotic stress response. However, the function of YABBY gene family in lettuce (Lactuca sativa), an important leaf vegetable is still unclear yet. Results: In this study, we analyzed the chromosomal distribution, gene structure and cis-transcriptional elements of the YABBY gene family in lettuce. Phylogenetic analysis of YABBY genes in lettuce, Arabidopsis, maize and rice classified them into five groups. In addition, the expression profile of YABBY genes in lettuce indicated that they may play distinct functions in different tissues and developmental processes. The subcellular localization analysis and transactivation assay showed that LsaYAB7 probably functions as a transcription factor in the nucleus. Furthermore, the ectopic expression of LsaYAB7 exhibited abaxially curled leaves, not only in Arabidopsis, but also in lettuce. Conclusion: Altogether, LsaYAB7 is a key functional gene in determining the adaxial-abaxial polarity of lettuce leaves. Our study laid foundation for the molecular research of functional genes in lettuce.