Structural, biochemical, and physiological characterization of C4 photosynthesis in species having two vastly different types of kranz anatomy in genus Suaeda (Chenopodiaceae).

C (4) species of family Chenopodiaceae, subfamily Suaedoideae have two types of Kranz anatomy in genus Suaeda, sections Salsina and Schoberia, both of which have an outer (palisade mesophyll) and an inner (Kranz) layer of chlorenchyma cells in usually semi-terete leaves. Features of Salsina (S. AEGYPTIACA, S. arcuata, S. taxifolia) and Schoberia type (S. acuminata, S. Eltonica, S. cochlearifoliA) were compared to C (3) type S. Heterophylla. In Salsina type, two layers of chlorenchyma at the leaf periphery surround water-storage tissue in which the vascular bundles are embedded. In leaves of the Schoberia type, enlarged water-storage hypodermal cells surround two layers of chlorenchyma tissue, with the latter surrounding the vascular bundles. The chloroplasts in Kranz cells are located in the centripetal position in Salsina type and in the centrifugal position in the Schoberia type. Western blots on C (4) acid decarboxylases show that both Kranz forms are NAD-malic enzyme (NAD-ME) type C (4) species. Transmission electron microscopy shows that mesophyll cells have chloroplasts with reduced grana, while Kranz cells have chloroplasts with well-developed grana and large, specialized mitochondria, characteristic of NAD-ME type C (4) chenopods. In both C (4) types, phosphoenolpyruvate carboxylase is localized in the palisade mesophyll, and Rubisco and mitochondrial NAD-ME are localized in Kranz cells, where starch is mainly stored. The C (3) species S. heterophylla has Brezia type isolateral leaf structure, with several layers of Rubisco-containing chlorenchyma. Photosynthetic response curves to varying CO (2) and light in the Schoberia Type and Salsina type species were similar, and typical of C (4) plants. The results indicate that two structural forms of Kranz anatomy evolved in parallel in species of subfamily Suaedoideae having NAD-ME type C (4) photosynthesis.

Molecular characterization and expression analysis of a highly conserved rice mago nashil homolog.

Mago Nashi, a protein initially shown to be essential in the development of the Drosophila oocyte, is highly conserved among species and shows no homology to any other known cellular proteins. Here we report the nucleotide sequence of a cDNA and a partial gene that encode rice Mago Nashi protein homologs. In addition, we present the tissue-specific expression pattern of mago nashi at the level of RNA and protein. The rice Mago Nashi protein shares at least 73% amino acid identity with all known animal homologs. Genomic DNA gel blot analysis indicates that two copies of the mago nashi gene exist in the rice genome, one of which has identical intron positions to those found in an Arabidopsis homolog. mago nashi is expressed in root, leaf and developing seed tissue as determined by RNA and protein gel blot analysis. Evidence from Drosophila, Caenorhabditis elegans and human studies of Mago Nashi suggests that a major function of this protein is its involvement in RNA localization. The highly conserved amino acid sequence of all Mago Nashi protein homologs across kingdoms suggests that the plant version of this protein may similarly be involved in RNA localization.

Developing prolamine protein bodies are associated with the cortical cytoskeleton in rice endosperm cells.

The mRNAs that encode the prolamine storage proteins in rice (Oryza sativa L.) endosperm cells are enriched on the surface of the prolamine protein bodies (PBs), a subcellular structure consisting of a prolamine intracisternal granule surrounded by rough endoplasmic reticulum membrane. Previous biochemical studies (D.G. Muench et al., 1998, Plant Physiol. 116: 559-569) have shown that prolamine mRNAs may be anchored to the PB surface via the cytoskeleton. To better understand the mechanism and role of mRNA localization in rice endosperm cells, we studied the subcellular development of prolamine PBs and their relationship with the cytoskeleton in rice endosperm cells. Confocal microscopy of endosperm cells showed that, unlike the glutelin PBs, the developing prolamine PBs are not randomly distributed within the cell, but instead are often enriched in the cortical region of the cell only a few micrometers beneath the plasma membrane. In addition, the peripheral prolamine PBs are closely associated with the cortical microtubule and actin filament networks. The cortical enrichment of rice prolamine protein bodies represents a unique example of endoplasmic reticulum subdomain localization in plant cells. The interaction of this endoplasmic reticulum subdomain with the cytoskeleton provides new insights on the possible mechanism and role of mRNA localization in plants.