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CABI Book Chapter

Amino acids in higher plants.

Book cover for Amino acids in higher plants.


This book, divided into 5 parts, deals with topics on amino acids in higher plants. Part I (enzymes and metabolism) contains 16 chapters pursuing the theme of amino acid metabolism through the driving actions of the principal enzymes, emphasizing recent advances particularly with reference to localization, biophysical characterization and regulation. Part II (dynamics) includes two chapters design...


Chapter 19 (Page no: 340)

Auxin biosynthesis.

Auxin biology has enjoyed a renaissance in recent years, with the recognition and elucidation of its role in gene regulation, and an understanding at the cell biology level of how gradients and concentration maxima are created in tissues via polar transport. However, many questions remain open, especially concerning the function of auxin as a morphogen and how auxin self-regulates aspects of its own transport. The major auxin in plants is indole-3-acetic acid (IAA), though other active forms exist as well, including 4-chloroindole-3-acetic acid and phenylacetic acid; there are also storage forms, which include indole-3-butyric acid. Only some auxin exists as free IAA; the reversible or non-reversible conjugation of IAA to amino acids, sugars or proteins plays an important role in auxin homeostasis and metabolism, and can either act as a storage pool for active auxin when required, or target it for degradation. In bacteria, auxin synthesis consists of a relatively simple, two-step pathway. In plants, most of the information on auxin synthesis derives from the model species Arabidopsis thaliana, in which mutants have partially elucidated some of these pathways, but other species, such as pea, maize and tobacco have also been informative. Four main biosynthetic pathways have been proposed in plants, and the prevailing view for many years has been that these function in parallel, with species- or tissue-specific differences. Auxin synthesis is thus complex, and little understood, as some of the enzymatic steps remain uncharacterized; also, some of the pathways of synthesis converge with those that produce other secondary metabolites, and it is unclear whether or not these are important for the majority of auxin production. Furthermore, there have been problems in correlating in vitro studies with in vivo substrates for some pathways. Nevertheless, recent work has clarified one complete pathway from Trp to IAA that is highly conserved across the plant kingdom and is, therefore, thought to be the major pathway for auxin production in higher plants. This pathway consists of two steps: the first is catalysed by tryptophan aminotransferase to convert Trp to indole-3-pyruvic acid; the second rate-limiting step uses the YUCCA (YUC) flavin monooxygenases to create IAA. Several important conclusions about auxin synthesis have been reached recently. First, its local synthesis in specific tissues is tightly regulated in response to the environment, and in tissue-specific and developmentally important time windows. A further level of regulation includes genetic redundancy, as many enzymes for different biosynthetic steps are encoded by multi-gene families in numerous species. Compartmentation is also important for synthesis: tryptophan is synthesized in the chloroplast and auxin in the cytoplasm, although one metabolic step is regulated by an alternatively spliced gene that encodes an enzyme that affects the intracellular compartmentation of auxin synthesis. Current understanding of the principal route to auxin production in plants is summarized here, together with the evidence for alternative routes. The regulation of auxin biosynthesis is described at genetic, transcriptional and environmental levels, and at the level of cross-talk by other hormones; there is also discussion of how homeostasis and conjugation determines the size of the active auxin pool. An awareness of auxin synthesis in different plant species allows aspects of conservation to be identified and informs evolutionary developmental biology debates on the origin of auxin synthesis. Understanding the conservation of the major auxin biosynthetic pathway might accelerate knowledge in crop species, for which less is currently known of the genes encoding the catalytic steps than in Arabidopsis; such an understanding might also facilitate targeted manipulation to optimize crop productivity.

Other chapters from this book

Chapter: 1 (Page no: 1) Glutamate dehydrogenase. Author(s): Osuji, G. O. Madu, W. C.
Chapter: 2 (Page no: 30) Alanine aminotransferase: amino acid metabolism in higher plants. Author(s): Raychaudhuri, A.
Chapter: 3 (Page no: 57) Aspartate aminotransferase. Author(s): Leasure, C. D. He, Z. H.
Chapter: 4 (Page no: 68) Tyrosine aminotransferase. Author(s): Hudson, A. O.
Chapter: 5 (Page no: 82) An insight into the role and regulation of glutamine synthetase in plants. Author(s): Sengupta-Gopalan, C. Ortega, J. L.
Chapter: 6 (Page no: 100) Asparagine synthetase. Author(s): Duff, S. M. G.
Chapter: 7 (Page no: 129) Glutamate decarboxylase. Author(s): Molina-Rueda, J. J. Garrido-Aranda, A. Gallardo, F.
Chapter: 8 (Page no: 142) L-arginine-dependent nitric oxide synthase activity. Author(s): Corpas, F. J. Río, L. A. del Palma, J. M. Barroso, J. B.
Chapter: 9 (Page no: 156) Ornithine: at the crossroads of multiple paths to amino acids and polyamines. Author(s): Majumdar, R. Minocha, R. Minocha, S. C.
Chapter: 10 (Page no: 177) Polyamines in plants: biosynthesis from arginine, and metabolic, physiological and stress-response roles. Author(s): Mattoo, A. K. Fatima, T. Upadhyay, R. K. Handa, A. K.
Chapter: 11 (Page no: 195) Serine acetyltransferase. Author(s): Watanabe, M. Hubberten, H. M. Saito, K. Hoefgen, R.
Chapter: 12 (Page no: 219) Cysteine homeostasis. Author(s): García, I. Romero, L. C. Gotor, C.
Chapter: 13 (Page no: 234) Lysine metabolism. Author(s): Medici, L. O. Nazareno, A. C. Gaziola, S. A. Schmidt, D. Azevedo, R. A.
Chapter: 14 (Page no: 251) Histidine. Author(s): Ingle, R. A.
Chapter: 15 (Page no: 262) Amino acid synthesis under abiotic stress. Author(s): Planchet, E. Limami, A. M.
Chapter: 16 (Page no: 277) The central role of glutamate and aspartate in the post-translational control of respiration and nitrogen assimilation in plant cells. Author(s): O'Leary, B. Plaxton, W. C.
Chapter: 17 (Page no: 298) Amino acid export in plants. Author(s): Price, M. B. Okumoto, S.
Chapter: 18 (Page no: 315) Uptake, transport and redistribution of amino nitrogen in woody plants. Author(s): Pfautsch, S. Bell, T. L. Gessler, A.
Chapter: 20 (Page no: 362) Involvement of tryptophan-pathway-derived secondary metabolism in the defence responses of grasses. Author(s): Ishihara, A. Matsukawa, T. Nomura, T. Sue, M. Oikawa, A. Okazaki, Y. Tebayashi, S.
Chapter: 21 (Page no: 390) Melatonin: synthesis from tryptophan and its role in higher plant. Author(s): Arnao, M. B. Hernández-Ruiz, J.
Chapter: 22 (Page no: 436) Glucosinolate biosynthesis from amino acids. Author(s): Stotz, H. U. Brown, P. D. Tokuhisa, J.
Chapter: 23 (Page no: 448) Natural toxins that affect plant amino acid metabolism. Author(s): Duke, S. O. Dayan, F. E.
Chapter: 24 (Page no: 461) Glyphosate: the fate and toxicology of a herbicidal amino acid derivative. Author(s): Saltmiras, D. A. Farmer, D. R. Mehrsheikh, A. Bleeke, M. S.
Chapter: 25 (Page no: 481) Amino acid analysis of plant products. Author(s): Rutherfurd, S. M.
Chapter: 26 (Page no: 497) Metabolic amino acid availability in foods of plant origin: implications for human and livestock nutrition. Author(s): Levesque, C. L.
Chapter: 27 (Page no: 507) Toxicology of non-protein amino acids. Author(s): D'Mello, J. P. F.
Chapter: 28 (Page no: 538) Delivering innovative solutions and paradigms for a changing environment. Author(s): D'Mello, J. P. F.

Chapter details

  • Author Affiliation
  • Institute of Developmental Biology, Cologne Biocenter, Cologne University, Cologne, Germany.
  • Year of Publication
  • 2015
  • ISBN
  • 9781780642635
  • Record Number
  • 20153121429