A MYB-WRKY feedback module activates MdAAT2‑like to regulate aromatic ester biosynthesis during apple ripening

Area of Science:

• Plant Biochemistry
• Molecular Biology
• Fruit Science

Background:

• Aromatic esters significantly impact apple fruit aroma and consumer acceptance.
• Understanding the genetic regulation of ester biosynthesis is crucial for improving fruit quality.

Purpose of the Study:

• To elucidate the molecular mechanisms controlling ester biosynthesis in apple.
• To characterize the function and regulation of the apple ester-synthesizing gene MdAAT2-like.

Main Methods:

• Gene expression analysis during apple fruit ripening.
• Functional validation of MdAAT2-like in apple and tomato via overexpression and gene silencing/knockout.
• Enzymatic assays to determine substrate specificity.
• Identification and characterization of transcription factors regulating MdAAT2-like.

Main Results:

• MdAAT2-like expression and ester content increased during fruit ripening.
• Overexpression of MdAAT2-like boosted ester production, while silencing/knockout reduced it.
• MdAAT2-like showed high catalytic efficiency for medium- and short-chain acyl-CoAs.
• MdMYB98-like and MdWRKY21 directly activate MdAAT2-like transcription and reciprocally activate each other, forming a positive feedback loop.

Conclusions:

• MdAAT2-like is a critical enzyme in apple ester biosynthesis.
• A MYB-WRKY regulatory module (MdMYB98-like and MdWRKY21) controls MdAAT2-like expression.
• This regulatory network promotes rapid ester synthesis during fruit ripening, enhancing apple aroma.