PLANT PHYSIOLOGY , Vol 109, Issue 2 525-531, Copyright © 1995 by American Society of Plant Biologists
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GENE REGULATION AND MOLECULAR GENETICS |
Polyphenol Oxidase in Potato (A Multigene Family That Exhibits Differential Expression Patterns)
P. W. Thygesen, I. B. Dry and S. P. Robinson
Division of Horticulture, Commonwealth Scientific and Industrial Research Organisation, GPO Box 350, Adelaide, South Australia, 5001, Australia
Polyphenol oxidase (PPO) activity in potato (Solanum tuberosum) plants was
high in stolons, tubers, roots, and flowers but low in leaves and stems.
PPO activity per tuber continued to increase throughout tuber development
but was highest on a fresh weight basis in developing tubers. PPO activity
was greatest at the tuber exterior, including the skin and cortex tissue 1
to 2 mm beneath the skin. Flowers had high PPO activity throughout
development, particularly in the anthers and ovary. Five distinct cDNA
clones encoding PPO were isolated from developing tuber RNA. POT32 was the
major form expressed in tubers and was found in all parts of the tuber and
at all stages of tuber development. It was also expressed in roots but not
in photosynthetic tissues. POT33 was expressed in tubers but mainly in the
tissue near the skin. POT72 was detected in roots and at low levels in
developing tubers. NOR333 was identical with the P2 PPO clone previously
isolated from potato leaves (M.D. Hunt, N.T. Eannetta, Y. Haifeng, S.M.
Newman, J.C. Steffens [1993] Plant Mol Biol 21: 59-68) and was detected in
young leaves and in tissue near the tuber skin but was highly expressed in
flowers. The results indicate that PPO is present as a small multigene
family in potato and that each gene has a specific temporal and spatial
pattern of expression.
