The tomato 66.3-kD polyphenoloxidase gene: molecular identification and developmental expression

Area of Science:

• Plant Molecular Biology
• Developmental Biology
• Genetics

Background:

• Floral meristems are critical for plant reproduction, and understanding their development is key to plant science.
• Polyphenol oxidases (PPOs) are enzymes involved in various plant processes, but their specific roles in floral meristem development are not fully elucidated.

Purpose of the Study:

• To isolate and characterize a gene encoding a polypeptide abundant in tomato floral meristems.
• To investigate the expression patterns of this gene in different plant tissues and developmental stages.
• To determine the role of the identified gene in distinguishing floral from vegetative meristems.

Main Methods:

• Gene isolation and characterization using cDNA and genomic clones.
• Analysis of polypeptide structure, including conserved copper-binding domains.
• Transcript and polypeptide accumulation studies in wild-type and mutant tomato plants (anantha mutant).
• Expression analysis in floral primordia, developing floral organs, and young leaves.

Main Results:

• A gene for a 66.3-kD polyphenoloxidase (PPO), designated P2, was isolated from tomato.
• The P2 polypeptide contains conserved copper-binding domains characteristic of tyrosinases.
• P2 transcripts and polypeptides accumulate in floral primordia of both wild-type and anantha mutant tomatoes, and in developing floral organs.
• P2 protein is also found in palisade cells and epidermal trichomes of young leaves.
• Expression patterns of P2 allow for molecular distinction between floral and vegetative meristems.

Conclusions:

• The identified PPO gene (P2) is highly expressed in tomato floral meristems and developing floral organs.
• P2 expression serves as a molecular marker to differentiate floral from vegetative meristems in tomato.
• P2, along with dUTPase, may indicate alternative developmental programs in plant meristems.