Advances in determination of polymer structure and in preservation of structure for electron microscopy provide the best view to date of how polysaccharides and structural proteins are organized into plant cell walls. The walls that form and partition dividing cells are modified chemically and structurally from the walls expanding to provide a cell with its functional form. In grasses, the chemical structure of the wall differs from that of all other flowering plant species that have been examined. Nevertheless, both types of wall must conform to the same physical laws. Cell expansion occurs via strictly regulated reorientation of each of the wall's components that first permits the wall to stretch in specific directions and then lock into final shape. This review integrates information on the chemical structure of individual polymers with data obtained from new techniques used to probe the arrangement of the polymers within the walls of individual cells. We provide structural models of two distinct types of walls in flowering plants consistent with the physical properties of the wall and its components.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.1993.tb00007.x

Structural models of primary cell walls in flowering plants: consistency of molecular structure with the physical properties of the walls during growth

Auxin: regulation, action, and interaction.

http://genomics.unl.edu/RBC_2012/COURSE_FILES/mon2.pdf

Thioredoxin and glutaredoxin systems

Long-standing models propose that plant growth responses to light or gravity are mediated by asymmetric distribution of the phytohormone auxin. Physiological studies implicated a specific transport system that relocates auxin laterally, thereby effecting differential growth; however, neither the molecular components of this system nor the cellular mechanism of auxin redistribution on light or gravity perception have been identified. Here, we show that auxin accumulates asymmetrically during differential growth in an efflux-dependent manner. Mutations in the Arabidopsis gene PIN3, a regulator of auxin efflux, alter differential growth. PIN3 is expressed in gravity-sensing tissues, with PIN3 protein accumulating predominantly at the lateral cell surface. PIN3 localizes to the plasma membrane and to vesicles that cycle in an actin-dependent manner. In the root columella, PIN3 is positioned symmetrically at the plasma membrane but rapidly relocalizes laterally on gravity stimulation. Our data indicate that PIN3 is a component of the lateral auxin transport system regulating tropic growth. In addition, actin-dependent relocalization of PIN3 in response to gravity provides a mechanism for redirecting auxin flux to trigger asymmetric growth.

/pdf/lateral-relocation-of-auxin-efflux-regulator-pin3-mediates-2qn76qi1lq.pdf

Lateral relocation of auxin efflux regulator PIN3 mediates tropism in Arabidopsis

Publisher Summary The fibroblast growth factors (FGFs) constitute a family of closely related polypeptide mitogens There are seven members of this family, identified on the basis of amino acid sequence homologies The FGF family has distinguished itself from other growth factor families by virtue of the pleiotropic actions of its members This chapter discusses the structural and functional diversity in the FGF receptor multigene family The effects of FGFs are known to be mediated by high-affinity receptor tyrosine kinases The structurally diverse receptor molecules are also functionally different The characterization of structural and functional diversity within the FGF receptor shows the differences in the mechanisms of action among members of the FGF family The first members of the FGF family to be purified and characterized were acidic FGF (aFGF) and basic FGF (bFGF), which are purified on the basis of their mitogenicity toward fibroblasts by using bovine pituitary Functional differences among the different receptor forms are observed in the chapter at two levels The long-range goal of designing the effective agonist and antagonists of FGF action has considerable therapeutic value

Structural and Functional Diversity in the FGf Receptor Multigene Family

The chromatographic identification of some biologically important phosphate esters.

Enzymatic reactions involving sulfate, sulfite, selenate, and molybdate.

Seeds of oat, coconut, soybean, sunflower, rice, millet, kidney bean, buckwheat, wheat, and corn and vegetative tissue of oat, pea, and corn were assayed for free indole-3-acetic acid (IAA), esterified IAA, and peptidyl IAA. Three conclusions were drawn: (a) all plant tissues examined contained most of their IAA as derivatives, either esterified or as a peptide; (b) the cereal grains examined contained mainly ester IAA; (c) the legume seeds examined contained mainly peptidyl IAA. Errors in analysis of free and bound IAA are discussed.

Concentration of Indole-3-acetic Acid and Its Derivatives in Plants.

Plants contain most of the growth hormone indole-3-acetic acid (IAA) in conjugated forms believed to be inactive in promoting growth. The iaglu gene, which controls the first step in the biosynthesis of the IAA conjugates of Zea mays, encodes (uridine 5'-diphosphate-glucose:indol-3-ylacetyl)-beta-D-glucosyl transferase. Protein synthesized by Escherichia coli that contained cloned 1-O-beta-D-indol-3-ylacetyl-glucose complementary DNA (cDNA) was catalytically active. The predicted amino acid sequence of the cDNA was confirmed by amino-terminal sequencing of the purified enzyme. Homologous nucleotide sequences were found in all plants tested. The blockage or enhancement of iaglu expression may permit regulation of plant growth.

iaglu, a gene from Zea mays involved in conjugation of growth hormone indole-3-acetic acid

The amounts and rates of metabolic turnover of the indolylic compounds in germinating kernels of sweet corn were determined. Knowledge of pool size and rate of pool turnover has permitted: ( a ) identification of indole-3-acetyl- myo -inositol as the major chemical form for transport of indole-3-acetic acid (IAA) from endosperm to shoot; ( b ) demonstration that the free IAA of the endosperm is turning over rapidly with a half-life of 3.2 hours; ( c ) identification of esters of IAA as the immediate precursors of IAA in the endosperm and shoot; ( d ) demonstration that neither tryptophan nor tryptamine is a major precursor of IAA for the seed or shoot; ( e ) identification of IAA- myo -inositol glycosides as precursors of IAA- myo -inositol. It is concluded that seedlings of Zea mays utilize esters of IAA, and not tryptophan or its derivatives, for the IAA requirements of the germinating seedling.

Robert S. Bandurski

Papers

The chromatographic identification of some biologically important phosphate esters.

Enzymatic reactions involving sulfate, sulfite, selenate, and molybdate.

Concentration of Indole-3-acetic Acid and Its Derivatives in Plants.

iaglu, a gene from Zea mays involved in conjugation of growth hormone indole-3-acetic acid

Concentration and Metabolic Turnover of Indoles in Germinating Kernels of Zea mays L.