Complex N-Glycans Are Important for Normal Fruit Ripening and Seed Development in Tomato

Area of Science:

• Plant Biology
• Glycobiology
• Molecular Plant Science

Background:

• Complex N-glycan modification is essential in animals but its role in plants, particularly in fruit development, is less understood.
• While Arabidopsis mutants lacking N-acetyl-glucosaminyltransferase I (GNTI) are viable, rice mutants show developmental defects, suggesting species-specific roles.
• Previous research aimed to reduce allergenic potential by targeting core fucose and xylose residues in N-glycans.

Purpose of the Study:

• To investigate the role of complex N-glycan maturation in tomato (Solanum lycopersicum) development and fruit production.
• To analyze the effects of reduced activity of N-acetyl-glucosaminyltransferase I (GNTI) and Golgi alpha-mannosidase II (MANII) on tomato phenotypes.
• To explore the connection between N-glycan modification and plant hormone signaling pathways.

Main Methods:

• RNA interference (RNAi) was used to reduce GNTI and MANII activity in tomato plants.
• Phenotypic analysis included observations of fruit development, ripening, abscission, seed set, and leaf morphology.
• Semiquantitative RT-PCR was employed to assess gene expression related to abscission and auxin response.
• Phytohormone levels and 1-aminocyclopropane-1-carboxylic acid (ACC) were measured.

Main Results:

• Reduced GNTI activity led to necrotic fruit stalks, premature fruit drop, and incomplete ripening, with increased abscission markers.
• MANII-reduced plants exhibited normal fruit attachment but had underdeveloped seeds and curled leaf rims, with failed cross-breeding attempts.
• Auxin-responsive gene expression differed in GNTI-RNAi plants, suggesting a role for N-glycans in hormone signaling.
• While ethephon and IAA could not rescue GNTI-RNAi phenotypes, IAA mimicked patchy ripening in wild-type.

Conclusions:

• Complex N-glycan maturation, particularly via GNTI, is vital for normal tomato fruit development, abscission, and ripening.
• MANII plays a role in seed development and leaf morphology, with its reduction impacting reproductive viability.
• Altered N-glycan structures may influence plant hormone signaling, particularly auxin pathways, affecting developmental processes.
• These findings highlight the importance of complex N-glycan biosynthesis for crop yield and development in fruit-bearing plants.