Lycopene is an important carotenoid pigment in fruits and vegetables,
especially in tomato. While lycopene synthesis is known to be regulated by
multiple factors, little is known about their regulation.
Isopentenyltransferases (IPTs) are known to catalyze the initial
rate-limiting step in the synthesis of cytokinin, an important hormone
involved in various aspects of plant growth. However, the other roles of
IPTs remain unclear.

A research team led by Yong Zhang from Chongqing University in China studied
the function of the SlIPT4 gene, which encodes an isopentenyltransferase,
using RNAi-mediated gene silencing in tomato. As expected, silencing of
SlIPT4 resulted in accelerated leaf senescence. However, silencing of SlIPT4
also generated never-red orange fruits, suggesting a dramatic reduction in
lycopene. Among the lycopene synthesis-related genes, the ZISO gene was
found to have significantly reduced expression.

This study revealed that SlIPT4 positively regulates lycopene biosynthesis
by affecting the expression of the ZISO gene. SlIPT4 also has crucial roles
in leaf senescence. This provides a new light on lycopene biosynthesis in
tomato.



[bmcplantbiol.biomedcentral.com]