PLANT PHYSIOLOGY , Vol 109, Issue 2 385-392, Copyright © 1995 by American Society of Plant Biologists

DEVELOPMENT AND GROWTH REGULATION

Molecular and Ultrastructural Analysis of a Nonchromosomal Variegated Mutant (Tomato Mitochondrial Mutants That Cause Abnormal Leaf Development)

A. B. Bonnema, C. Castillo, N. Reiter, M. Cunningham, H. P. Adams and M. O'Connell
Graduate Program in Molecular Biology, Department of Agronomy and Horticulture (A.B.B., C.C., N.R., M.O.'C), and Electron Microscopy Laboratory (M.C., H.A.), New Mexico State University, Las Cruces, New Mexico 88003-0003

Mutants were recovered in a population of cybrids formed following protoplast fusion between tomato (Lycopersicon esculentum Mill.) cv UC82 and Lycopersicon pennellii Corr. The cybrids were identified as individuals with recombinant cytoplasmic genomes but only tomato nuclear genomes. The mutants were identified based on two features, a variegated sectoring of light and dark green regions on their leaves, stems, and fruit, and reduced growth in the field. The mutants produced 50% of the shoot fresh weight and 20% of the fruit fresh weight of the parental type, UC82. The variegated sectoring was maternally inherited. The chloroplast genome in the mutants was indistinguishable from the chloroplast genome in UC82, when distribution of restriction endonuclease sites was used as an assay. The mitochondrial genome in the mutants, however, was recombinant, containing genes from UC82 and L. pennellii. Light microscopic analysis of the leaves of the mutants demonstrated an absence of the palisade layer in the variegated sectors. Electron microscopic analysis of these same regions demonstrated an absence of normal inner membranes in the mitochondria of these cells.