Ectopic Expression And Functional Analysis Of AtmiR399f In Tomato

Phosphorus (P) is an essential element for plant growth and development. It plays important roles in energy transfer, signal transduction, photosynthesis, and respiration and is a structural component of nucleic acids and phospholipids. In soil solution, inorganic phosphorus (Pi) is readily available to most crops at a limited concentration. Recently, a new type of regulatory element, miR399, has been found in the P starvation response. AtmiR399-overexpressing Arabidopsis accumulates more P in shoots, and the transcript level of two phosphate transporter genes are upregulated in AtmiR399-overexpressing plants.MicroRNA is highly conserved both in sequence and function in different plants. To examine if miR399 functions in tomato, a fragment of AtmiR399f gene was amplified from Arabidopsis and introduced into tomato with Agrobacterium-mediated transformation. Two transgenic lines with different expression levels of AtmiR399f gene were chosen to identify the function of miR399 in tomato. The results showed that two transgenic tomato lines produced larger seeds and increased stem diameter than the control. Meanwhile, miR399 oversuply altered root architecture. Transgenic tomatoes produced a highly branched root system with abundant lateral and secondary lateral roots to enhance the tolerance to low phosphorus. In addition, AtmiR399f overexpression increased the transcript abundancy of several genes associated with ethylene synthesis, indicating that miR399 positively modulate ethylene in tomato.