Potato plants with genetically engineered tropane alkaloid precursors.

Area of Science:

• Plant biochemistry
• Alkaloid biosynthesis
• Molecular genetics

Background:

• Calystegines are hydroxylated alkaloids found in potato roots and tubers.
• Their function in plants remains unclear, despite their in vitro inhibition of glycosidases.
• The tropane alkaloid pathway is responsible for calystegine formation.

Purpose of the Study:

• To investigate the roles of key enzymes in calystegine biosynthesis in Solanum tuberosum.
• To elucidate the specific functions of putrescine N-methyltransferase (PMT) and tropinone reductases (TRI, TRII) in this pathway.

Main Methods:

• Genetic manipulation of potato plants using RNA interference (RNAi) and overexpression.
• Altering the activity of PMT, TRI, and TRII enzymes.
• Quantifying calystegine accumulation and related intermediates in transformed plants.

Main Results:

• Overexpression of putrescine N-methyltransferase (PMT) did not affect calystegine levels.
• Solanum tuberosum tropinone reductase I (StTRI) activity was confirmed in vivo, but did not influence calystegine accumulation.
• Suppression of StTRII via RNAi severely reduced calystegine formation in potato sprouts.

Conclusions:

• StTRII plays a critical role in calystegine biosynthesis in potato.
• StTRI is functional but not rate-limiting for calystegine production.
• Calystegine-deprived potato plants (StTRII RNAi) provide a model for studying calystegine functions under natural conditions.