Differential Expression of the Ribulose Bisphosphate Carboxylase Large Subunit Gene in Bundle Sheath and Mesophyll Cells of Developing Maize Leaves Is Influenced by Light

Abstract

We have investigated the influence of light on the mRNA of the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase in mesophyll and bundle sheath cells of the C4 plant Zea mays. The gene is transcribed in both cell types in leaves of seedlings grown in the dark. However, upon illumination, the level of mRNA declines and becomes undetectable in mesophyll cells after 72 hours. On the contrary, in bundle sheath cells the two transcripts of the same gene increase to peak after 24 hours of greening and then decrease to a steady state level. This study was made possible by the development of improved methods for the isolation of two maize leaf cell types suitable for the extraction of high quality RNAs at different developmental states, i.e. etiolated, greening and green.Transcripts of six regions comprising about 19% of the maize chloroplast chromosome increase in abundance during lightinduced maturation of etioplasts in dark-grown seedlings into photosynthetically competent chloroplasts (11). One of these regions carries the genes for RuBPCase LS2 as well as the fused DNA sequences coding for the ,8-E CF,. The levels of transcripts of these CF, and RuBPCase genes accumulate to a maximum level after about 20 h of greening and then drop in abundance (4,(10)(11)(12). However, maize is a C4 plant thus photosynthetic carbon fixation is the result of the coordinated activities of MC and BSC. In mature green leaves of maize, the mRNA for the fl-E CF, is abundant in chloroplasts of both MC and BSC, but that for the large subunit of RuBPCase is present only in the latter I

Subpopulations of chloroplast ribosomes change during photoregulated development of Zea mays leaves: Ribosomal proteins L2, L21, and L29

“…As is shown in the representative Western blots in The relative amounts of a ribosomal protein present in a given cell type under different conditions were calculated from densitometer scans of four Western blots of proteins in ribosomal pellets. Extracts were prepared from MC and BSC isolated from dark-grown unilluminated or illuminated (10 hr) plants (7). Ribosomal pellets were prepared by centrifugation of ribosomes through 1 M sucrose cushions (18).…”

Photomorphogenic Responses in Maize Seedling Development

“…Plants were then placed in one of four light conditions (R, FR, B, or D) for 48 h. Tissue was harvested under dim-green safe lights for all light treatments except the W control, which was performed in ambient light. M and BS cells were then isolated as previously described with some modifications (Sheen and Bogorad, 1985).…”

Characterization of the Expression of the Photosystem II-Oxygen Evolving Complex in C4 Species of Flaveria

“…In addition, the expression of some enzymes, e.g. Rubisco, requires the coordinate synthesis and assembly of subunits encoded by two separate genomes (chloroplast and nuclear) (4,15,25,26,28).…”

“…This pattem was in contrast to the three-to tenfold higher levels of transcripts encoding photosystem 11 polypeptides in mesophyll versus bundle sheath cells of maize. It is apparent that the higher mesophyll cell to bundle sheath ratio of photosystem 11 polypeptides in C4-and C4-like species of Flaveria is the result of higher levels of photosystem 11 expression in mesophyll cells rather than lower levels of expression in bundle sheath cells.generation ofelevated CO2 concentrations in the BSC, leading to a reduction in photorespiratory activities (6).The tissue-specific expression of C3 and C4 cycle enzymes is determined by developmentally regulated processes as well as by environmental (light) signals and may be regulated at the transcriptional and/or posttranscriptional level (4,10,12,15,20,23,25,28). In addition, the expression of some enzymes, e.g.…”

“…In addition, the expression of some enzymes, e.g. Rubisco, requires the coordinate synthesis and assembly of subunits encoded by two separate genomes (chloroplast and nuclear) (4,15,25,26,28).To date, the molecular characterization of the expression of multi-subunit enzyme complexes in C4 plants has largely focused on this two subunit enzyme complex, Rubisco (4,25,27). Another multi-subunit enzyme complex that is expressed in a tissue-specific manner in NADP-ME type C4 plants is 11,26,28).…”