Self-fertile apple resulting from S-RNase gene silencing

Area of Science:

• Plant Biotechnology
• Reproductive Biology
• Horticultural Science

Background:

• Self-incompatibility (SI) is a genetic mechanism that prevents self-fertilization in many plant species, including apple.
• SI systems in fruit crops limit fruit set and seed production, impacting agricultural yields.
• The S-gene and its associated S-RNase proteins control the SI response in apple.

Purpose of the Study:

• To develop self-fertile apple trees by genetically modifying the endogenous S-gene.
• To investigate the effect of extra S-gene copies on self-pollination success and fruit development.
• To understand the molecular mechanisms underlying self-fertility in transgenic apple lines.

Main Methods:

• Generation of transgenic apple trees with additional copies of the S-gene.
• Controlled self- and cross-pollination experiments over three years.
• Microscopic analysis of pollen tube growth within the pistil.
• Biochemical analysis of S-RNase protein presence in pistils.

Main Results:

• Transgenic apple lines exhibited normal fruit and seed set after self-pollination, unlike control trees.
• Pollen tube growth was uninhibited in self-pollinated transgenic pistils, whereas it was inhibited in controls.
• The self-fertile phenotype in transgenic lines correlated with the absence of pistil S-RNase proteins.

Conclusions:

• Genetic modification of the S-gene successfully induced self-fertility in apple trees.
• Inhibition of S-RNase expression in the pistil is the key mechanism for achieving self-fertility.
• This research provides a foundation for enhancing fruit set and yield in self-incompatible tree fruit crops.