Elevated CO<Subscript>2</Subscript> influences host plant defense response in chickpea against <Emphasis Type="Italic">Helicoverpa armigera</Emphasis>

Global atmospheric concentration of CO₂ is likely to increase from 350 to 750 ppm over the next 100 years. The present studies were undertaken to understand the effects of elevated CO₂ on enzymatic activity and secondary metabolites in chickpea in relation to expression of resistance to pod borer, Helicoverpa armigera. Fifteen-day-old chickpea plants [ICCL 86111—resistant and JG 11—commercial cultivar] grown in the greenhouse were transferred to open-top chambers (OTC) and kept under 350, 550 and 750 ppm of CO₂. Twenty neonates of H. armigera were released on each plant at 7 days after shifting the pots to the OTCs. Un-infested plants were maintained as controls. After 7 days of infestation, the activities of defensive enzymes [peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) and tyrosine ammonia lyase (TAL)] and amounts of total phenols and condensed tannins increased with an increase in CO₂ concentration in chickpea. The nitrogen balance index was greater in plants kept at 350 ppm CO₂ than in plants kept under ambient conditions. The H. armigera-infested plants had higher H₂O₂ content; amounts of oxalic and malic acids were greater at 750 ppm CO₂ than at 350 ppm CO₂. Plant damage was greater at 350 ppm than at 550 and 750 ppm CO₂. This information will be useful for understanding effects of increased levels of CO₂ on expression of resistance to insect pests to develop strategies to mitigate the effects of climate change.     

Coexistence of multiple peptides in small intensely fluorescent (SIF) cells of inferior mesenteric ganglion of the guinea pig

Summary Coexistence of peptides in the small intensely fluorescent cells was demonstrated by immunocytochemistry for met-enkephalin-Arg-Gly-Leu, vasoactive intestinal polypeptide, somatostatin, neuropeptide Y and dynorphin. In the extreme example, a single cell was immunoreactive to all 5 peptides examined. Four peptides coexisted in 8% and three peptides in 13% of SIF cells. In 10% of SIF cells no peptide immunoreactivity could be detected. The most prevalent peptide was met-enkephalin (in 46% of cells), then vasoactive intestinal polypeptide (45%), somatostatin (39%), neuropeptide Y (31%) and dynorphin (24%). Met-enkephalin and vasoactive intestinal polypeptide coexisted most commonly (25%).     

Storage-protein hydrolysis and protein-body breakdown in germinatedZea mays L. seeds

Storage proteins of maize (Zea mays L.) were studied in germinated seeds, as were the proteins of protein bodies isolated from endosperms at different germination times. Major endosperm storage proteins were degraded in a sequential way, glutelin 2 being hydrolysed faster than zein 1. Immunocytochemical labelling of the different protein bodies using the antisera anti-glutelin 2 and anti-zein 1 indicates that the protein bodies were degraded by progressive hydrolysis from their surface. The digestion of glutelin 2 correlated with the disappearance of the protein-body membranes.     

Differential expression of a hydroxyproline-rich cell-wall protein gene in embryonic tissues of Zea mays L.

A hydroxyproline-rich glycoprotein (HRGP) component of the maize cell wall was shown to be present in different organs of the plant by extraction of cell wall proteins and detection by Western blotting and immunocytochemistry. Antibodies raised against the protein or against synthetic peptides designed from the protein sequence immunoprecipitated a proline-rich polypeptide which was synthesized in-vitro from poly(A) ⁺ RNA extracted from different tissues of the plant and from the complete in-vitro-transcribed mRNA. A very low amount of the protein was found in immature embryos. In particular, the protein could not be detected in the scutellum either by Western blotting or by immunocytochemistry. In agreement with this finding, HRGP mRNA was barely detected in the scutellum, in contrast to its accumulation in the embryo axis. Our results indicate the existence of a unique cell wall structure in embryonic tissues from maize as well as a tissuespecific component of the control of maize HRGP gene expression, distinct to others already described such as cell division.Abbreviations HRGP(s) hydroxyproline-richglycoprotein(s) - DAP days after pollination The present work was supported by grants from Plan Nacional de Investigation Cientifica y Técnica (grant BI088-0242) and European Communities (grant BAP-374). L.R.-A. is the recipient of a fellowship from the Plan Nacional de Formación de Personal Investigador.     

Early and late passage C-6 glial cell growth: Similarities with primary glial cells in culture

Earlier studies in our laboratory have shown that C-6 glial cells in culture exhibit astrocytic properties with increasing cell passage. In this study, we tested the responsiveness of early and late passage C-6 glial cells to various cultures conditions: culture substrata (collagen, poly-L-lysine, plastic), or supplements for the culture medium, DMEM, [fetal calf, or heat inactivated (HI) serum, or media conditioned from mouse neuroblastoma cells (NBCM) or primary chick embryo cultured neurons (NCM)]. Glutamine synthetase (GS) and cyclic nucleotide phosphohydrolase (CNP), astrocytic and oligodendrocytic glial markers, were used. Cell numer and protein content increased exponentially with days in culture regardless of the type of the substratum or cell passage. Differences in cell morphology among the three types of substratum were also reflected on GS activity, which rose by three-fold on culture day 3 for cells grown on collagen; thereafter, GS profiles were similar for all substrata. This early rise in GS is interpreted to reflect differential cell adhesion processes on the substrata; specifically, cell adhesion on the collagen stimulated differentiation into astrocytic phenotype.Analogous to immature glia cells in primary cultures, early passage C-6 glial cells responded to neuronal factors supplied either from NCM or NBCM by expressing reduced GS activity, the astrocytic marker and enhanced CNP activity, the oligodendrocytic marker. Thus, early passage cells can be induced to express either astrocytic or oligodendrocytic phenotype. In accordance with our previous reports on primary glial cells, late passage C-6 cells exhibit their usual astrocytic behavior, responding to serum factors with GS activity. Moreover, whereas NCM or NBCM alone markedly lowered GS activity, a combination with serum restored activity. The present findings confirm our previous observations and further establish the C-6 glial cells as a reliable model to study immature glia.Special issue dedicated to Dr. Paola S. Timiras.     

Expression of a maize cell wall hydroxyproline-rich glycoprotein gene in early leaf and root vascular differentiation.

The spatial pattern of expression for a maize gene encoding a hydroxyproline-rich glycoprotein (HRGP) was determined by in situ hybridization. During normal development of roots and leaves, the expression of the gene was transient and particularly high in regions initiating vascular elements and associated sclerenchyma. Its expression was also associated with the differentiation of vascular elements in a variety of other tissues. The gene encoded an HRGP that had been extracted from the cell walls of maize suspension culture cells and several other embryonic and post-embryonic tissues. The gene was present in one or two copies in different varieties of maize and in the related monocots teosinte and sorghum. A single gene was cloned from maize using a previously characterized HRGP cDNA clone [Stiefel et al. (1988). Plant Mol. Biol. 11, 483-493]. In addition to the coding sequences for the HRGP and an N-terminal signal sequence, the gene contained a single intron in the nontranslated 3' end.