DNA and RNA Levels in Bundle Sheath and Mesophyll Cells of Pearl Millett (Pennisetum americanum)

Abstract

The DNA content of bundle sheath cells and mesophyll protoplasts from the C4 plant pearl millet (Pennisetum americanum, Tift 23DB) was determined by microspectrophotometry to be 1.8 to 2.3 and 3.2 to 4.0 picograms/nucleus, respectively. Measurement of RNA by ultraviolet spectroscopy indicated that bundle sheath cells contain twice as much RNA as mesophyll cells.A common assumption among researchers is that nuclear DNA contents are the same in cells of mature, differentiated plant tissues comprising a given organ. Reports in the literature, however, suggest caution in applying this assumption to diverse experimental systems. For example, Evans and Van't Hof (15) compared ploidy levels in various tissues of three angiosperm genera. No polyploid cells were found in any tissue of Helianthus annuus examined, but polyploidy in Pisum sativum tissues was the rule, rather than the exception. Likewise, cells in the cotyledons of developing soybean seedlings differed significantly in DNA content depending on the age of the tissue sampled (13). These results indicate that individual cells within a single tissue may differ in nuclear DNA content, as may tissues within a single organ. The primary objective of our work, therefore, was to compare the relative DNA and RNA contents of the two photosynthetically active cell types, bundle sheath and mesophyll, in the leaves of the C4 grass pearl millet. The limitations and possible significance of these results are presented here, and the difference in nuclear DNA content between the cell types is discussed in light of current information about cell differentiation, cell cycle progression, and the role of polyploidy in plant growth and development. MATERIALS AND METHODS

Nuclear DNA Content and Ploidy Levels in the Genus Ipomoea

“…Instrument or operator variance during nuclear isolation and analysis also could be responsible for different measured values. Although the source of variation is unknown in the following example, DNA content measurements by two groups (Arumuganathan and Earle, 1991a;Michelson et al, 1991), both using propidium iodide as the DNA fluorochrome, gave differences in 2C DNA amounts as high as 1 pg for Helianthus annuus L. and Gossypium hirsutum L. Finally, within-plant differences also have been reported as developmental modifications (Bassett et al, 1988;Bassi, 1990;Cavallini and Natali, 1991). Conceivably, the estimation of DNA content in different organs could be the source of some reported variation.…”

A Common Histone Modification Code on C4 Genes in Maize and Its Conservation in Sorghum and Setaria italica

“…3A). A rapid mechanical isolation protocol at low temperatures was used for B cell preparation in order to minimize hnRNA turnover during the preparation (Jenkins and Boag, 1985;Bassett et al, 1988). We did not isolate M cells for this assay, because the preparation of M cell protoplasts from leaves is a lengthy procedure during which C4 genes are often strongly suppressed.…”

Changes in DNA level of growing barley seedlings

“…Lamppa and Bendich (1984) reported that the total cellular DNA in mature pea leaves consisted of 0.9% mitochondrial and 12% chloroplast DNA. Bassett et al (1988) reported that the DNA contents of bundle sheath cells and mesophyll protoplasts from pearl millet were different. Although these factors should be taken into account, we can more precisely discuss the results obtained from experiments in relation to plant nutrition and physiology by expressing the data on a unit DNA weight basis.…”