Although our model is highly speculative, experiments are under way to test several of the predictions generated. DOI: https://doi.org/10.1105/tpc.11.5.849. In C3 plant both Mesophyll cells and Bundle sheath cells have Rubisco while in C4 plant only Bundle sheath However, further genomic restriction mapping identified a 2.8-kb SstI-SalI Mu8-hybridizing fragment that was also linked to the bsd2-m1 mutant allele. Compared with terrestrial plants, submerged aquatic plants lack A) leaves. The ectopic accumulation of rbcL transcripts in mesophyll cells of leaves of light-grown bsd2 plants (Roth et al., 1996) as well as misexpression in dark-grown leaves suggest that BSD2 may regulate rbcL gene expression. DOI: https://doi.org/10.1104/pp.103.4.1183. This question is for testing whether or not you are a human visitor and to prevent automated spam submissions. The association of rbcL transcripts with large polysomes in the mutant plants indicated that BSD2 is unlikely to play a role in translation initiation or the early steps of elongation (see Klein et al., 1988). It combines with CO 2 in presence of an enzyme Phosphoenol pyruvate carboxylase (PEPCase) and forms a C4 combines with CO 2 in Therefore, the striking similarity between BSD2 and this domain of DnaJ suggests that BSD2 may play a role in preventing aggregation or misfolding of nascent polypeptides. A wheat germ cell-free lysate was used to translate mRNA derived by T3 RNA polymerase–driven transcription of a full-length Bsd2 cDNA clone. As we have suggested, BSD2 appears to regulate rbcL gene expression. Incubation was for 60 min in the light. Because [CO2] in bundle sheath cells of inhibited leaves is likely to be much lower than ambient, the lack of O2 sensitivity of CO2 uptake cannot be ascribed to lack of O2 reaction with ribulose bisphosphate and is probably due to 3C,D), which occasionally leads to an overlap of cells and a double cell layer for a short distance. (C) Schematic representation of the bsd2 locus. Abstract. However, previous studies with Mu (Barkan and Martienssen, 1991) have shown that weak promoter elements exist in the terminal inverted repeats of the Mu transposon. Thank you for your interest in spreading the word on Plant Physiology. (C) Hybridization to RNA isolated from purified bundle sheath strands (BS) and mesophyll cell protoplasts (M). What purpose are the air spaces in the spongy mesophyll? Significantly, this fragment was absent in the progenitor lines from which bsd2-m1 plants were generated (Figure 1A, lanes 1 and 2). As shown in Figure 5A, Bsd2 transcripts were localized to shoot tissues and were relatively abundant in etiolated, light-shifted, and young (plastochron 1 to 5) leaves of wild-type plants but were present at greatly reduced levels in the mutant. Immunoblot Analysis of Nucleus- and Chloroplast-Encoded Proteins in Wild-Type (Bsd2) and Mutant (bsd2) Plants. C) stomata. If the Bsd2 gene has a direct role in regulating rbcL gene expression, it may be expected to show a similar expression profile to the rbcL gene. Stromal and thylakoid fractions were then run on a gel. Bundle sheath cells lack chloroplasts. Enter multiple addresses on separate lines or separate them with commas. T.P.B. This work was supported by grants to J.A.L. A clearer picture has been obtained for the export of photosynthates. To look at the role of BSD2 in chloroplast import, we also examined C4 photosynthetic enzyme accumulation patterns. wild-type leaf tissue (Figures 8B and 8C) suggested that correct chloroplast targeting and processing occurs in both bundle sheath and mesophyll cells of bsd2 plants. Differential Sensitivity of Chloroplasts in Mesophyll and Bundle Sheath Cells in Maize, an NADP-Malic Enzyme-Type C_4 Plant, to Salinity Stress HASAN Rusdi , OHNUKI Youichiro , KAWASAKI Michio , TANIGUCHI Mitsutaka , MIYAKE Hiroshi Plant production science 8(5), 567-577, 2005-12-01 This results in a reduced photorespiration rate. RNA gel blot analysis of total RNA probed with Bsd2.1 (see Figure 1C) failed to identify a transcript in wild-type or bsd2-m1 individuals (data not shown). Sites of polyadenylation are underlined. Plastochron 1-5 tissue was collected by harvesting tissue 2 to 3 mm above the meristem before emergence of the first leaf from the coleoptile. Consequently, bundle sheath chloroplasts swell, and internal thylakoid membranes break down in the light. The Bsd2.2 fragment was used to screen a maize leaf cDNA library, and several cDNA clones were isolated. DNA from progenitor lines PL and PM (lanes 1 and 2, respectively) or from sibling wild-type plants (lanes 3 to 6) and bsd2 mutants (lanes 7 to 9) was digested with SstI and fractionated on an 0.8% agarose gel before transfer to a nylon membrane.