Pathways of Respiration in Plant Tumors

Abstract

Altered pathways of respiration in plants after infection with fungi, particularly obligate fungal pathogens, are well documented (27), but little is known about plant respiration after infection by bacterial pathogens. Agrobacterium tumefaciens, a bacterial pathogen with a wide plant host range, has the ability to permanently alter host cells to tumor cells (9). Information on the respiratory pathways of these altered cells is of interest to plant pathologists for its possible significance in over-all disease symptoms and to students of oncology.The following reports have appeared in the literature on respiratory pathways of these tissues. Brucher and Schmidt (11) added inhibitors of glycolysis and the tricarboxylic acid cycle to in vitro grown normal and tumor tissues of Datura and carrot and concluded that the importance of respiration via glycolyis and the tricarboxylic acid cycle is reduced in tumor tissues. The inadequacies of inhibitor studies have been stressed (22). In vitro cultures of normal and tumor tomato tissues were studied by Tamaoki and coworkers (36) who showed that mitochondria isolated from such materials possessed the ability to oxidize tricarboxylic acid cycle intermediates and to perform oxidative phosphorylations. Both the rate of oxidation and the P/O ratios were less in mitochondria isolated from tumors.A different approach to investigating respiratory pathways in tumor tissues was adopted in the present work. The activities of enzymes of the hexose monophosphate shunt, glycolysis, and the tricarboxylic acid cycle were determined in homogenates of normal and tumor tissues of red beet roots. In addition, the dissimilation of glucose specifically labeled in the -1, -2, or -6 position was examined in these tissues. The results obtained are discussed in relation to the relative importance of the hexose monophosphate shunt and glycolysis in both tissues. '

Glycolytic enzyme pattern and constant proportion group in plant cells as related to their developmental and functional state

“…Both in root and coleoptile all activities increased several-fold during elongation, reached maximal [9,121). Our data on enzyme activities per g fresh weight and mg protein are in good agreement with those for pea cotyledons [ 181 and parenchyma tissues of red beet roots (except PFK, PGK, and PK) [2] and potato tubers [3,191 ; Per cell levels of PFK and PK in root tip of pea seedlings (calculated on the basis of data [4] ) and in suspension of Acerpseuduplatanus cells [lo] correspond to those in maize root tip, however, GAPDH level in pea roots and GAPDH and PGK levels in Acer were much lower than in maize.…”

“…all 5 enzymes in beet [2] , PGK/GAPDH in developing wheat seedlings [ 111 and dividing Acer cells [lo] , TIM/GAPDH in germinating pine seeds [20], and more variable TIM, PGK, PGM, and PPG ratios in derepressed potato tuber tissue [3, 191. …”

Influence of Nutrition on the Activities of some Enzymes of glycolysis and the Pentose Phosphate Pathway in Expanding Lucerne Leaves

“…1.1.1.49), and phosphogluconate dehydrogenase (PGDH; E.C. 1.1.1.43) were assayed according to Scott, Craigie, and Smillie (1964). All assays were carried out at 25°C in a final reaction volume of 3 ml.…”

Effects of Indoleacetic Acid and Kinetin on Activities of Enzymes of the Hexose Monophosphate Shunt in Tissue Cultures of Nicotiana

“…It has been reported that the activities of glucose-6-P dehydrogenase, 6-P-gluconate dehydrogenase, and phosphoriboisomerase are enhanced in plant tumor cells compared with normal cells (8). This raises the possibility that the increased activities of HMP shunt enzymes5 are linked with the increased availability of hormones in the plant tumor cells.…”

“…This raises the possibility that the increased activities of HMP shunt enzymes5 are linked with the increased availability of hormones in the plant tumor cells. The following investigation was designed to determine whether IAA PLANT PHYSIOLOGY of assay for these enzymes was the samle as previously described (8). All (2) who observed increasedl activities of glucose-6-P (lehydrogenase and 6-P-gluconate (lehyclrogenase in root tips of corn seedlings after treatment with 2,4-D. Apart from using different plant mlaterial the concentration of hormones usecl by these wx3rkers was 10 al which was much higher than in the present inivestigationi and( their time of exposure of the tissues to the hormlonies was only 12 hours.…”