Table 2.
Summarization of key findings with specific features of tomato GRF genes for organ development, abiotic stresses response, and different phytohormones treatment with their structural characteristics and phylogenetic classification.
| Observation on | Key Findings and Predicted Specific Function (s) Based on Expression Data | |
|---|---|---|
| Structural characteristics | 13 GRF genes were identified from Solanum lycopersicum. All of them contained functional QLQ and WRC domain and diverge C-terminal region rich in Pro, Gln, Ser/Thr that are frequently found in transcription factors. Besides, some of SlGRF contained C-terminal FFD and TQL motifs. The structural characteristics suggested that SlGRF proteins function as transcriptional regulators. | |
| Phylogenetic classification | The GRF proteins from tomato, potato, Arabidopsis, Chinese cabbage, rice and maize phylogenitically classified into nine subfamilies which indicated their ancestral evolution and tomato GRF proteins are more closely related to potato suggested their evolution from common ancestor. | |
| Relative expression in different organs/tissues | Among the 13 SlGRF genes one gene; SlGRF9 was undetectable in all organ studied and suggested as pseudogene. The organ expression analysis revealed that most of the genes predominantly expressed in flower bud indicating possible function in flower bud (i.e., reproductive organ development) in tomato. The SlGRF genes also showed differential expression in meristem, full blooming flower, leaf, stem, root, seedling and in different fruit developmental stages suggesting the important function in growth and development of tomato. The relatively higher expression of 12 SlGRF genes in different organs are listed below: |
|
| SlGRF1: | Flower bud, meristem and ripening fruit | |
| SlGRF2: | Flower bud, meristem, flower blooming and small green fruit | |
| SlGRF3: | Flower bud, meristem, flower blooming and small green fruit | |
| SlGRF4: | Flower bud | |
| SlGRF5: | Flower bud, meristem and small green fruit | |
| SlGRF7: | Flower bud and meristem | |
| SlGRF8: | Flower bud | |
| SlGRF10: | Flower bud, meristem and ripening fruit | |
| SlGRF11: | Flower bud and meristem | |
| SlGRF12: | Meristem, leaf, flower bud, small green fruit | |
| SlGRF13: | Meristem, leaf, flower bud, seedling, stem, and small green fruit | |
| Relative expression under abiotic stresses and phytohormone treatments | Four abiotic stresses—NaCl, drought, heat, cold and three phytohormones (GA3, ABA, and JA) treatments—were studied where the following genes were (up/down) regulated by abiotic and phytohormone treatments at different time points: | |
| SlGRF1: | NaCl, drought, heat, cold, JA | |
| SlGRF2: | NaCl, drought, heat, cold, ABA, GA3, JA | |
| SlGRF3: | NaCl, drought, heat, cold, ABA, GA3, JA | |
| SlGRF4: | NaCl, drought, heat, cold, ABA, GA3, JA | |
| SlGRF5: | NaCl, drought, heat, cold, ABA, GA3 | |
| SlGRF6: | NaCl, drought, heat, cold, ABA, GA3, JA | |
| SlGRF7: | NaCl, drought, ABA, GA3, JA | |
| SlGRF10: | Drought, heat, cold, ABA, JA | |
| SlGRF11: | Drought, heat, cold, JA | |
| SlGRF12: | Drought, heat, cold, ABA, JA | |
| SlGRF13: | Drought, heat, cold, ABA, JA | |