Changes in protein synthesis induced in tomato by chilling

Area of Science:

• Plant Physiology
• Molecular Biology
• Photosynthesis Research

Background:

• Dark chilling significantly inhibits net photosynthesis in tomato plants, primarily due to impaired chloroplast function.
• Tomato plants can recover photosynthetic capacity after chilling when rewarmed in darkness under high humidity.

Purpose of the Study:

• To identify potential sites of chilling injury in tomato by monitoring leaf protein synthesis during the rewarming recovery phase.
• To understand the molecular mechanisms underlying chilling-induced photosynthetic impairment and recovery.

Main Methods:

• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of pulse-labeled proteins to analyze changes in synthesis.
• Peptide mapping and immunoprecipitation to identify specific proteins.
• Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) to characterize newly synthesized proteins.

Main Results:

• Chilling reduced the synthesis of a 27 kilodalton (kD) protein, identified as the major chlorophyll a/b binding protein of photosystem II light-harvesting complex (LHCP-II).
• Chilling induced the synthesis of a novel 35 kD protein, synthesized on cytoplasmic ribosomes and distinct from LHCP-II.
• Chilling selectively reduced the synthesis of thylakoid membrane proteins, including the beta-subunit of chloroplast coupling factor.

Conclusions:

• The decline in LHCP-II synthesis is a key indicator of chilling injury affecting photosynthesis.
• The chilling-induced 35 kD protein may play a role in the plant's response to low temperatures.
• Reduced synthesis of specific thylakoid proteins likely contributes to the overall decrease in net photosynthesis observed after chilling.