Photosynthetic Enzyme Accumulation during Leaf Development of Arundinella hirta, a C4 Grass Having Kranz Cells not Associated with Veins

Abstract

The leaf of the NADP-malic enzyme type C(4) grass, Arundinella hirta, has not only mesophyll cells (MCs) and bundle sheath cells (BSCs, usual Kranz cells) but also another type of Kranz cells (distinctive cells; DCs) that are not associated with vascular bundles. We investigated photosynthetic enzyme accumulation along the base-to-tip maturation gradient of developing leaves by immunogold electron microscopy. In mature leaves, phosphoenolpyruvate carboxylase (PEPC) and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) were detected in the MC cytosol and in the BSC and DC chloroplasts, respectively. Pyruvate, P(i) dikinase (PPDK) was present in the chloroplasts of all photosynthetic cells but with higher levels in the MCs. Rubisco was first detected in the basal region of emerging leaf blades where the BSCs and DCs became discernable. Subsequently, the accumulation of PEPC and PPDK was initiated in the region where the granal proliferation in the chloroplasts was conspicuous; and, suberized lamellae were formed in the cell walls of the Kranz cells. There was no difference in the patterns of cellular development and enzyme accumulation between the BSCs and DCs or between the MCs adjacent to each type of Kranz cells. These results demonstrate that, although the DCs are not associated with veins, they behaved like BSCs with respect to enzyme induction and cellular differentiation.

Structure and enzyme expression in photosynthetic organs of the atypical C4 grass Arundinella hirta

“…3m-o). Although the chloroplasts in the BSCs of the leaf blade were centrifugally located (Crookston and Moss 1973;Dengler et al 1996;Wakayama et al 2003), there was a tendency that those of the other organs were irregularly located: somewhat centrifugal in some cases (Fig. 3a), but scattered in the BSCs in many cases (Fig.…”

“…C. Tanaka were collected in the field in Saitama City, Japan, and were propagated from tillers (Wakayama et al 2003). Plants were grown in potted, sufficiently fertilized field soil in a growth chamber with a light-dark cycle of 25°C for 14 h and 20°C for 10 h. Artificial illumination was provided by metal-halide lamps at 300 lmol m À2 s À1 (wavelength 400-700 nm).…”

“…Antiserum against the large subunit (LS) of Rubisco from pea leaves was a kind gift of the late Dr. S. Muto (Nagoya University, Nagoya, Japan). These antisera were the same as those used in our previous study on the leaf blades of Arundinella hirta (Wakayama et al 2003).…”

“…These cells are called distinctive cells (DCs) (Tateoka 1958). Previous studies of the cellular distribution of photosynthetic enzymes have revealed that DCs have a BSC-like photosynthetic function (Reger and Yates 1979;Ueno 1995;Wakayama et al 2003). The DCs run longitudinally, forming single-cell files or multiple-cell strands in the mesophyll tissue between the veins, when seen in paradermal view (Dengler and Dengler 1990;Ueno 1995).…”

“…Extensive studies of Arundinella hirta leaves have shown that cellular differentiation (Dengler et al 1996;Wakayama et al 2003) and photosynthetic enzyme induction (Wakayama et al 2003) are indistinguishable between the BSCs and DCs, and between the MCs adjacent to them, suggesting that a vein-derived positional signal (Langdale and Nelson 1991;Dengler and Nelson 1999) is not essential for C 4 pattern expression.…”