To explore the possible regulatory roles of miRNAs in fleshy fruit ripening process, we select fruits at three different ripening periods (mature green stage, the breaker stage and red ripening stage) of the Solanum lycopersicum (Ailsa Craig).
Recent work has characterized the molecular mechanisms that govern the transition of tomato fruit from a green to a fully red ripe fruit, via the intermediate stages termed breaker, turning and pink.
MR1 was a mixture of equal amounts of RNA from stems and leaves, buds, flowers, and young fruit, while MR2-4 were fruit at breaker stage, red maturity stage, and dark red maturity stage, respectively.
The MR2-4 libraries consisted of separate RNA samples from fruit of three different ripening stages, i.e., 75 DAF (the breaker stage fruit), 80 DAF (red ripe stage fruit), and 85 DAF (dark red ripe stage fruit).
For the other samples, plants were grown in the greenhouse and the following tissues or organs were harvested: fully expanded leaves, flowers at anthesis, flowers two days post anthesis, developing fruits with 5 mm diameter, developing fruits with 18 mm diameter, mature green fruits, fruits at breaker stage, fruits at turning stage and fruit at red ripe stage.
We used mRNA isolated from: tomato seedlings, leaves, roots, flowers at anthesis, flowers at 2 days post anthesis (DPA), immature green fruit at two sizes (5 mm diameter and 18 mm diameter, respectively), mature green fruit, breaker stage fruit, turning stage fruit, and red ripe fruit.
The SlCOBRA-like gene was highly expressed during the early stages of fruit development, but the expression level dramatically declined after the breaker stage, indicating a role in early fruit development.
In addition, the fruit traits that were studied included single fruit weight, diameter, and height; fruit shape index (h/d ratio) and in the breaker stage [ 46]; fruit number per inflorescence; fruiting stage; maturity stage; and fruit setting rate.
Nevertheless, several genes show dramatic increase at the breaker stage compared to the immature stage.
Fruit firmness dropped from the breaker stage until the red ripe stage, correlating well to the ripening process.
