Planta 148, 108 115 (1980) Planta 9 by Springer-Verlag 1980 Rearrangement of Enzyme Patterns in Maize Callus and Suspension Cultures Is it Relevant to the Changes in the Growing Cells of the Intact Plant? Inessa V. Zeleneva and Emil E. Khavkin Siberian Institute of Plant Physiology and Biochemistry, Siberian Branch, Academy of Sciences of USSR, P.O. Box 1243, Irkutsk 33, USSR 664033 Abstract. The development of enzyme patterns was followed in the course of: (a) the irreversible cell differentiation via division and expansion to maturity in the root tip and coleoptile of the intact seedlings, (b) the irreversible cell dedifferentation associated with induction and establishment of callus from the growing internodes, and (c) the growth cycle (prolifer- ationS-stationary phase) in callus and cell-suspension cultures of maize (Zea mays L.). By measuring the activities of glycolytic, mitochondrial, microbody and hydrolytic enzymes cells proliferating in vivo and in vitro could be compared and changes related to cessa- tion or resumption of cell division could be studied. Proliferating cells of callus and suspension cul- tures maintained by serial culture did not differ from those of the root meristem and coleoptile in the spe- cific activities of hexokinase, phosphoglycerate kinase and phosphopyruvate hydratase. Proliferation in vitro resulted in an enormous increase in the ratio gluta- mate-dehydrogenase/cytochrome-oxidase activity and in the level of acid-phosphatase activity, with concom- itant drop in galactosidase and xylosidase activity. A 3-5-fold increase of alcohol-dehydrogenase, lac- tate-dehydrogenase and catalase activities was charac- teristic of dividing callus cells, while a ca. 100-fold in- crease in the fructofuranosidase-to-glucosidase activ- ity ratio marked cell proliferation in suspension- cultured cells. Changing enzyme activities after cessation of pro- liferation were quite similar in root tips and coleop- tiles, except those of alcohol dehydrogenase and cat- alase. The enzyme rearrangement during callus estab- lishment and in the growth cycle of callus cultures was in most cases comparable to that in the intact tissues, while the changes from the dividing to the non-dividing cells in suspension cultures, in contrast, differed widely from those in the intact tissues and callus. Galactosidase and xylosidase were the only activities that showed a similar trend of changes in all the investigated, intact and in-vitro-grown cells. Thus, judged by the pattern of enzyme develop- ment, the cell suspension appears to be a unique sys- tem, virtually unrelated to the growing cells of the intact tissues. It is also very difficult to draw a definite distinction between the metabolic consequences of cell growth and enzyme modulations in cell suspensions as the cells adapt their metabolism to the environmen- tal changes in liquid medium. Key words: Callus - Cell proliferation - Cell suspen- sion - Coleoptile - Cytodifferentiation - Dedifferenti- ation - Enzyme profile Internode - Root tip - Zea. Introduction For biochemical studies of plant growth, tissue cul- ture provides unique possibilities to unravel the role of cell interactions inherent to the highly organized growth patterns in intact tissues, and to investigate the effects of the metabolic status upon cell growth and differentiation. Cell dedifferentiation during callus initiation seems to be a well-established fact. However, it is not altogether clear how to classify the progress of the cell in the course of the growth cycle in vitro, i.e., in proliferation, stationary phase and senescence: whether this progress to any extent resembles the normal sequence of biochemical events in the growing zones of intact plants, or whether it should rather be regarded as a mimicry of normal cytodifferentiation as suggested by Street (1977). These and several other aspects of tissue and cell cultures employed as a "model" in plant growth studies have been widely discussed in the two last decades (see Butenko, 1975, and Street, 1977, for re- cent reviews). As far as enzyme profiles of cells are concerned, some data have been produced on nucleic acid and sucrose metabolism in calli as compared 0032-0935/80/0148/0108/$01.60