How Loquats Protect Themselves with Sugar: A UV-B Defense Story

Ever wondered how plants protect themselves from sunburn? Loquats, also known as Japanese medlars, have a clever trick up their sleeves (or rather, leaves and fruits). They make special compounds called flavonol glycosides. These compounds help plants grow and defend against stress, like harsh UV-B rays. The final step in making these flavonol glycosides is handled by enzymes called UDP-glycosyltransferases, or UGTs for short. In loquats, these UGTs have been hiding in plain sight, until now. Scientists took a close look at loquat tissues and found 13 different flavonol glycosides. When loquat fruits get a tan from UV-B rays, the levels of quercetin and kaempferol glycosides go up. By studying the loquat's UGT genes and finding out what they do, scientists discovered three key players. EjUGT78T4 is like the painter, adding a galactose sugar to flavonols. EjUGT78S3 prefers glucose, while EjUGT91AK7 goes for a rhamnose. This artwork happens in the fruit and helps loquats survive under the sun's intense gaze. Understanding how these UGTs work helps explain how loquats form flavonol glycosides. It's like they're wearing sunscreen to shield themselves from UV-B rays!