Leaves of tomato plants (Lycopersicon esculentum cv. Fukuju no.2) inoculated with TMV-L11A (attenuated) or TMV-L (virulent) were compared by electron microscopy during the course of virus infection. Estimates were also made of the numbers of virions, the chlorophyll (a+b) content and the chlorophyll (a/b) ratio. Five days after inoculation, no differences were found in chloroplast structure, chlorophyll content or chlorophyll (a/b) ratio between healthy and infected plants, although a large number of virions were observed in these plants with both strains. From 10 to 30 days post-inoculation, changes in chlorophyll content and chlorophyll (a/b) ratios became apparent, the amount being in the order healthy>L11A>L. Virion accumulation was also much greater in cells infected with L than that with L11A. In both cases, chloroplasts were swollen and finally often ruptured. Their lamellar systems, however, remained essentially undamaged. Even though the L11A never induced mosaic symptoms, this attenuated strain also caused some ultrastructural changes in chloroplasts.
Direction and degree of plastid development in the tissue differentiation of sporangiogenesis inThelypteris palustris were studied, and are discussed through aspects of the plastome continuity and cell differentiation. Particular attention was paid to proplastid reproduction and segregative allocation of the plastids at the first division of the sporangial initial cell. Nascent proplastids were separately located in the outer cell for further generative differentiation. Preexisting chloroplasts were allocated to the inner cell as further vegetation cells of sporangium. Proplastids in the generative cells were followed by retarded processing of development, then transformed to amyloplasts in sponrocyte differentiation. The amyloplasts were noted due to their significance for direct transmittance of plastome to following generationsvia spores, while well developed functional chloroplasts were characterized as ending up in the ephemeral terminal of sporangial vegetative tissues.
The ultrastructural changes in plastids ofBuxus sempervirens L. leaves were observed during their seasonal yellowing and regreening. The disintegration of chloroplasts into globular type chromoplasts in yellowing leaves and their direct restoration to functional chloroplasts again in regreening leaves were followed. The results presented an example of recent information indicating the essential sense of the reversible reciprocation of plastid transformation.
To gain an overview of plant factors controlling nodule number and organogenesis, an extensive screening using model legume Lotus japonicus was carried out. This screening involved 40,000 M2 seeds, and 32 stable mutant lines were isolated. From these, 16 mutant lines maintaining the phenotypic variation were selected and genetically analyzed. With respect to nodule number, four loci were identified, Ljsym77, Ljsym78, slippery root (slp), and radial organization1 (rdo1). The former two mutants have an increased number of nodules, while the latter two have a decreased number. Ljsym78-1 and Ljsym78-2 are hypernodulating mutants with a branched root system and were found to be allelic to Ljsym16. The phenotype of the Ljsym77 mutant was highly pleiotropic, being deficient in light and gravity responses. The slp mutant was isolated as a low-nodulating mutant lacking root hairs. Concerning nodule organogenesis, nine symbiotic loci were identified, including the two loci alb1 and fen1. Mutants affecting the developmental process of nodule organogenesis were placed in three phenotypic categories: Nod¯ (Ljsym70 to Ljsym73), Hist¯ (alb1-1, alb1-2, and Ljsym79), and Fix¯ (fen1, Ljsym75, and Ljsym81).
The cyanide‐resistant alternative oxidase (AOX) is a homodimeric protein whose activity can be regulated by the oxidation/reduction state and by α‐keto acids. To further clarify the role of AOX in the skunk cabbage, Symplocarpus renifolius , we have performed expression and functional analyses of the encoding gene. Among the various tissues in the skunk cabbage, SrAOX transcripts were found to be specifically expressed in the thermogenic spadix. Moreover, our data demonstrate that the SrAOX protein exists as a non‐covalently associated dimer in the thermogenic spadix, and is more sensitive to pyruvate than to other carboxylic acids. Our results suggest that the pyruvate‐mediated modification of SrAOX activity plays a significant role in thermoregulation in the skunk cabbage.
