Structure and immunocytochemical localization of photosynthetic enzymes in the lamina joint and sheath pulvinus of the C4 grass Arundinella hirta

Abstract

The C(4) grass Arundinella hirta exhibits a unique C(4) anatomy, with isolated Kranz cells (distinctive cells) and C(4)-type expression of photosynthetic enzymes in the leaf sheath and stem as well as in the leaf blade. The border zones between these organs are pale green. Those between the leaf blade and sheath and between the sheath and stem are called the lamina joint and sheath pulvinus, respectively, and are involved in gravity sensing. We investigated the structure and localization of C(3) and C(4) photosynthetic enzymes in these tissues. In both zones the epidermis lacked stomata. The inner tissue was composed of parenchyma cells and vascular bundles. The parenchyma cells were densely packed with small intercellular spaces and contained granal chloroplasts with large starch grains. No C(4)-type cellular differentiation was recognized. Western blot analysis showed that the lamina joint and pulvinus accumulated substantial amounts of phosphoenolpyruvate carboxylase (PEPC), pyruvate,Pi dikinase (PPDK), and ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco). Immunogold electron microscopy revealed PEPC in the cytosol and both PPDK and rubisco in the chloroplasts of parenchyma cells, suggesting the occurrence of C(3) and C(4) enzymes within a single type of chlorenchyma cell. These data indicate that the lamina joint and pulvinus have unique expression patterns of C(3) and C(4) enzymes, unlike those in C(4)-type anatomy.

Structure and photosynthetic metabolism in green prop roots of C4 sorghum

“…In another C 4 eudicot Cleome angustifolia, the pods exhibit C 3 photosynthesis (Voznesenskaya et al, 2018). On the other hand, the lamina joint and sheath pulvinus of the C 4 grass Arundinella hirta seem to operate a C 4 -like cycle in a single type of chlorenchyma (Wakayama et al, 2013). Our study on prop roots of sorghum also demonstrates organ-specific expression of C 3 and C 4 photosynthetic types in roots and leaves.…”

“…Previous studies have reported that leaf sheath, spikes, husks, and stems of some C 4 grasses show Kranzlike anatomy, although the structural features were somewhat or greatly modified from that of leaf blades (Langdale et al, 1988;Pengelly et al, 2011;Wakayama et al, 2006). The structure of chlorenchyma of the AG portion was rather similar to those of the lamina joint and sheath pulvinus of the C 4 grass Arundinella hirta, in which the chlorenchyma is composed of a single type of cell (Wakayama et al, 2013). As expected, the BG portion of prop roots, which is not exposed to sunlight, lacked chloroplasts.…”

“…The following antisera were used for an immunohistochemical study and Western blot of the C 3 and C 4 enzymes: anti-pea leaf Rubisco large subunit (LSU) antiserum (courtesy of S. Muto, Nagoya University, Nagoya, Japan) and anti-maize leaf PEPC and PPDK antisera (courtesy of T. Sugiyama, RIKEN). These antisera were the same as those used in previous studies (Wakayama et al, 2006;Wakayama et al, 2013). The antisera were used at a dilution of 1:1000 for Rubisco LSU and 1:500 for PEPC and PPDK.…”