Inositol metabolism has special importance in plant biology.

Recent Advances in Phytochemisty, Volume 8: Metabolism and Regulation of Secondary Plant Products covers papers from the 13th annual meeting of the Phytochemical Society of North America held on August 8-10, 1973, at the Asilomar State Park and Conference Center in Pacific Grove, California. The book discusses phenylalanine ammonia-lyase and phenolic metabolism; enzymology and regulation of flavonoid and lignin biosynthesis in plants and plant cell suspension cultures; and possible multienzyme complexes regulating the formation of C6-C3 phelonic compounds and lignins in higher plants. The text also describes photoregulation of phenylpropanoid and styrylpyrone biosynthesis in Polyporis hispidus; the nonprotein amino acids from plants; and the role of proteinase inhibitors in natural plant protection. The regulatory control mechanisms in alkaloid biosynthesis; the biochemistry of myoinositol in plants; and unusual fatty acids in plants are also considered. Phytochemists and people involved in the study of pomology will find the book useful.

`The heterogeneity of topics ... is very ambitious, and the result is, overall, successful because of the high quality of the individual contributions ... highly recommended.' -American Scientist, from a review of a previous volume Volume 26 examines the emerging areas of signal transduction based on myoinositol phosphates and Ca2+ while focusing on plant and animal responses. Chapters explore synthesis, separation, and identification of different inositol phosphates.

This volume describes the current status of the biology of inositols and phosphoinositides with an emphasis on the development in the area since the publication of volume 26 in 1996 in this series. The progress made in dissecting the genetics, structure and evolution of the seminal enzyme for synthesis of inositol in the biological system has driven the understanding of the enzyme forward. With the current genomic and proteomic tools in place the new role of inositols, inositol phosphates and phosphoinositides in cell signaling or stress response has been explored. These advances are described in this volume and are expected to give new insights into the functional implications of inositol compounds across evolutionary diverse species.

An understanding of the mechanisms by which plants perceive environmental cues, both physical and chemical, and transduce the signals that influence specific expression of genes, is an area of intensive scientific research. With the completion of the genome sequence of Arabidopsis it is understood now that a larger number of genes encode for proteins involved in signalling cascades and transcription factors. In this volume, different chapters deal with plant receptors, second messengers like calcium ions, phosphoinositides, salicylic acid and nitrous oxide, calcium binding proteins and kinases. In addition to dealing with the response of plants to light, hormones, pathogens, heat, etc. on cellular activity, work currently going on in apoptosis, cell division, and plastid gene expression is also covered in this book.

The Chilton Conference on Inositol and Phosphoinositides, held on January 9-11, 1984 at Southwestern Medical School, University of Texas Health Science Center, Dallas, Texas, was the third in a series of conferences on cyclitols and phosphoinositides. The first took place in 1968 in New York [Ann. New York Acad. Sci. (1969), 765,508-819] and the second was held in 1977 in East Lansing, Michigan [eyclitols and Phosphoinositides, Wells, W. W. and Eisenberg, F. , eds. , (1978) Academic press, New York, pp. 1-607. ] In the interim since the previous conference, not only has the pace of research in the field accelerated markedly, but the physiological importance of phosphoinositide metabolism has become apparent to an increasing number of investigators from diverse fields in the life sciences. Thus it seemed to us timely for both recent and established workers in this area, as well as others whose interests impinged on it, to meet in order to disseminate new information, to review, and perhaps arrive at, a consensus of our current understanding of the role of inositol and phosphoinositides, and to establish new directions for research for the next few years. The expansion of the field since the last meeting made it mandatory to restrict the scope of the topics covered at the conference, primarily to aspects dealing with mammalian systems. We sincerely regretted the exclusion of recent research on cyclitols and phosphoinositides in microbes and plants and hope that these areas will be included in future conferences.

Occurrence and distribution of storage carbohydrates in vascular plants; Sucrose metabolism; Pathways and mechanisms associated with carbohydrate translocation in plants; Physiology and metabolism of sucrosyl-fructans; Biosynthesis of oligosaccharides in vascular plants; Physiology and metabolism of cyclitols; Physiology and metabolism of alditols; Biochemistry and physiology of synthesis of starch in leaves: autotrophic and heterotrophic chloroplasts; Degradation of starch in chloroplasts: a buffer to sucrose metabolism; Metabolism of reserve starch; Synthesis and degradation of extracellular storage polysaccharides.

The rhizopine concept sugests that rhizopines, which are inositol derivatives, function as nutritional mediators and play an important role in host-bacteria interactions. This thesis analyzes the hypothesis that not only rhizopines but also naturally occurring inositol isomers, such as myo-, D-chiro-, and scyllo-inositol, function as nutritional mediators in the Sinorhizobium meliloti-alfalfa nitrogen-fixing symbiosis. The idhA-encoded myo-inositol dehydrogenase is responsible for the first step in the degradation of myo- and D-chiro-inositol. A different dehydrogenase, IolY, was found to be essential for growth with scyllo-inositol. The iolA and iolCDEB genes were required for the further degradation of myo-, D-chiro- and scyllo-inositol. The idhA and iolA genes are monocistronically transcribed, while the iolYRCEB genes comprise an operon. The gene product of iolR, an RpiR-like repressor, negatively regulates iol gene expression in the absence of inositol. IolR was shown to recognize a conserved binding motif (5̕-GGAA5−11TTCC-3̕ ) in the promoter regions of the idhA and iolY genes. Two additional IolR-binding motifs were confirmed within the iolYRCDEB operon, upstream of iolR and iolC, indicating the the operon contains two internal operators and that IolR has autoregulatory function. IolR-mediated repression was antagonized by a pathway intermediate, probably 2-keto-5-deoxy-gluconic acid 6-phosphate. The iolA gene was not regulated by IolR, but constitutively expressed. The iolA gene product does not seem to be part of the central inositol catabolic pathway but rather a point of intersection of different metabolic pathways, including valine catabolism. The inositol derivative scyllo-inosamine (SIA) has been proposed to be a rhizopine. We used chemically snythesized SIA to confirm its proposed structure. The same genes essential for the degradation of crude rhizopine isolated from root nodules, namely the idhA and mocABCR genes were also found to be required for the utilization of the chemically synthesized SIA. In plant-bacteria interactions, mutants with insertions in the idhA, iolA, the individual iolYRCDE and mocACR genes could not compete with the wild type in a nodule occupancy assay on alfalfa plants. In conclusion, this work strongly supports the hypotesis that rhozipine and inositol metabolism are important nutritional and signaling factors in the S. meliloti-alfalfa symbiosis.

Inositol metabolism has special importance in plant biology.