Functional analysis of apple MhYTP1 and MhYTP2 genes in leaf senescence and fruit ripening

- MhYTP1 and MhYTP2 can be induced during natural leaf senescence in Malus.
- Overexpression of MhYTP1 or MhYTP2 promotes leaf senescence in Arabidopsis and Malus.
- Overexpression of MhYTP1 or MhYTP2 shortens the time to maturity for tomato fruits.
- MhYTP2 interacts with MhARD4, a protein involved in ethylene biosynthesis.

RNA binding proteins participate in many plant development processes and stress responses. Members of the YTH domain-containing RNA binding protein (YTP) family have been identified in apple (Malus × domestica Borkh.), and their stress responses have been investigated via quantitative real time PCR (qRT-PCR) methods. However, their functions in plant senescence have not been verified. Leaf senescence and fruit ripening can affect apple fruit quality. Thus, we cloned two homologous YTP family members in M. hupehensis, MhYTP1 and MhYTP2. These Group A1 members are localized to the entire cell. Expressions of MhYTP1 and MhYTP2 are induced during natural leaf senescence in Malus. The overexpression of either one can promote leaf senescence in Arabidopsis and Malus and promote fruit ripening in tomato. In addition, MhYTP2 interacts with an ethylene biosynthesis-related protein, acireductone dioxygenase 4 (MhARD4). Therefore, expression of MhYTP1 or MhYTP2 is positively correlated with plant senescence, suggesting that they can be used as marker genes for plant senescence. These results provide new information about senescence and can serve as a basis for further research that will help improve apple fruit quality.