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Legume-Rhizobium spp. symbiosis requires signaling between the symbiotic partners and differential expression of plant genes during nodule development. Previously, we cloned a gene encoding a putative/3-carotene hydroxylase (GmBCH1) from soybean (Glycine max) whose expression increased during nodulation with Bradyrhizobium japonicum. In this work, we extended our study to three GmBCHs to examine their possible role(s) in nodule development, as they were additionally identified as nodule specific, along with the completion of the soybean genome. In situ hybridization revealed the expression of three GmBCHs (GmBCH1, GmBCH2, and GmBCH3) in the infected cells of root nodules, and their enzymatic activities were confirmed by functional assays in Escherichia coil Localization of GmBCHs by transfecting Arabidopsis (Arabidopsis thaliana) protoplasts with green fluorescent protein fusions and by electron microscopic immunogold detection In soybean nodules indicated that GmBCH2 and GmBCH3 were present in plastids, while GmBCH1 appeared to be cytosolic. RNA interference of the GmBCHs severely impaired nitrogen fixation as well as nodule development. Surprisingly, we failed to detect zeaxanthin, a product of GmBCH, or any other carotenoids in nodules. Therefore, we examined the possibility that most of the carotenoids in nodules are converted or cleaved to other compounds. We detected the expression of some carotenoid cleavage dioxygenases (GmCCDs) in wild-type nodules and also a reduced amount of zeaxanthin in GmCCD8-expressing E. coli, suggesting cleavage of the carotenoid. In view of these findings, we propose that carotenoids such as zeaxanthin synthesized in root nodules are cleaved by GmCCDs, and we discuss the possible roles of the carotenoid cleavage products in nodulation. [ABSTRACT FROM AUTHOR]

Abstract We have characterized 4 of the 16 members of the family of dynamin-related proteins (DRP) in Arabidopsis. Three members, DRP1A (previously referred as ADL1), DRP1C and DRP1E, belong to the largest group of phragmoplastin-like proteins. DRP2A (ADL6) is one of the two members that contain a pleckstrin homology (PH) domain and a proline-rich (PR) motif, characteristics of animal dynamins. All four proteins interacted in yeast two-hybrid assays with phragmoplastin, and showed different patterns of localization at the forming cell plate during cytokinesis. GFP-tagged DRP1A and DRP1C proteins were found to be associated with the cytoskeleton in G1 phase of the cell cycle. The distribution pattern of DRP1A was sensitive to propyzamid and insensitive to cytochalasin D, suggesting that DRP1A is associated with microtubules and not actin filaments. The association of DRP1A with microtubules was confirmed in vitro by spin-down assays. A GTPase-defective phragmoplastin acted as a dominant negative mutant, reduced transport of vesicles to the cell plate and formed dense tubule-like structures in the cell plate. We propose that DRP1 proteins may provide an anchor for Golgi-derived vesicles to attach to microtubules, which in turn direct the vesicles to the forming cell plate during cytokinesis. Whereas the DRP1 subfamily members are involved in tubulization of membranes, DRP2 may be involved in endocytosis and membrane recycling via clathrin-coated vesicles. [ABSTRACT FROM AUTHOR]