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Pasricha Sarin L, Sree KS, Bóka K, Keresztes Á, Fuchs J, Tyagi AK, Khurana JP, Appenroth KJ. Characterisation of a Spontaneous Mutant of Lemna gibba G3 (Lemnaceae). PLANTS (BASEL, SWITZERLAND) 2023; 12:2525. [PMID: 37447086 DOI: 10.3390/plants12132525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 06/17/2023] [Accepted: 06/28/2023] [Indexed: 07/15/2023]
Abstract
A spontaneous mutant of the duckweed Lemna gibba clone no. 7796 (known as strain G3, WT) was discovered. In this mutant clone, L. gibba clone no. 9602 (mt), the morphological parameters (frond length, frond width, root length, root diameter) indicated an enlarged size. A change in the frond shape was indicated by the decreased frond length/width ratio, which could have taxonomic consequences. Several different cell types in both the frond and the root were also enlarged. Flow cytometric measurements disclosed the genome size of the WT as 557 Mbp/1C and that of the mt strain as 1153 Mbp/1C. This represents the results of polyploidisation of a diploid clone to a tetraploid one. The mutant clone flowered under the influence of long day-treatment in half-strength Hutner's medium in striking contrast to the diploid WT. Low concentration of salicylic acid (<1 µM) induced flowering in the tetraploid mutant but not in the diploid plants. The transcript levels of nuclear-encoded genes of the photosynthetic apparatus (CAB, RBCS) showed higher abundance in light and less dramatic decline in darkness in the mt than in WT, while this was not the case with plastid-encoded genes (RBCL, PSAA, PSBA, PSBC).
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Affiliation(s)
- Lakshmi Pasricha Sarin
- Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
| | - K Sowjanya Sree
- Department of Environmental Science, Central University of Kerala, Periye 671320, India
| | - Károly Bóka
- Department of Plant Anatomy, Eötvös Loránd University, H-1117 Budapest, Hungary
| | - Áron Keresztes
- Department of Plant Anatomy, Eötvös Loránd University, H-1117 Budapest, Hungary
| | - Jörg Fuchs
- The Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), 06466 Seeland, Germany
| | - Akhilesh K Tyagi
- Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
| | - Jitendra Paul Khurana
- Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
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Abramson BW, Novotny M, Hartwick NT, Colt K, Aevermann BD, Scheuermann RH, Michael TP. The genome and preliminary single-nuclei transcriptome of Lemna minuta reveals mechanisms of invasiveness. PLANT PHYSIOLOGY 2022; 188:879-897. [PMID: 34893913 PMCID: PMC8825320 DOI: 10.1093/plphys/kiab564] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 11/16/2021] [Indexed: 05/13/2023]
Abstract
The ability to trace every cell in some model organisms has led to the fundamental understanding of development and cellular function. However, in plants the complexity of cell number, organ size, and developmental time makes this a challenge even in the diminutive model plant Arabidopsis (Arabidopsis thaliana). Duckweed, basal nongrass aquatic monocots, provide an opportunity to follow every cell of an entire plant due to their small size, reduced body plan, and fast clonal growth habit. Here we present a chromosome-resolved genome for the highly invasive Lesser Duckweed (Lemna minuta) and generate a preliminary cell atlas leveraging low cell coverage single-nuclei sequencing. We resolved the 360 megabase genome into 21 chromosomes, revealing a core nonredundant gene set with only the ancient tau whole-genome duplication shared with all monocots, and paralog expansion as a result of tandem duplications related to phytoremediation. Leveraging SMARTseq2 single-nuclei sequencing, which provided higher gene coverage yet lower cell count, we profiled 269 nuclei covering 36.9% (8,457) of the L. minuta transcriptome. Since molecular validation was not possible in this nonmodel plant, we leveraged gene orthology with model organism single-cell expression datasets, gene ontology, and cell trajectory analysis to define putative cell types. We found that the tissue that we computationally defined as mesophyll expressed high levels of elemental transport genes consistent with this tissue playing a role in L. minuta wastewater detoxification. The L. minuta genome and preliminary cell map provide a paradigm to decipher developmental genes and pathways for an entire plant.
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Affiliation(s)
- Bradley W Abramson
- The Plant Molecular and Cellular Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Mark Novotny
- Department of Informatics, J. Craig Venter Institute, La Jolla, California 92037, USA
| | - Nolan T Hartwick
- The Plant Molecular and Cellular Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Kelly Colt
- The Plant Molecular and Cellular Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Brian D Aevermann
- Department of Informatics, J. Craig Venter Institute, La Jolla, California 92037, USA
| | - Richard H Scheuermann
- Department of Informatics, J. Craig Venter Institute, La Jolla, California 92037, USA
- Department of Pathology, University of California San Diego, La Jolla, California 92093, USA
- Division of Vaccine Discovery, La Jolla Institute for Immunology, La Jolla, California 92037, USA
| | - Todd P Michael
- The Plant Molecular and Cellular Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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Fourounjian P, Slovin J, Messing J. Flowering and Seed Production across the Lemnaceae. Int J Mol Sci 2021; 22:2733. [PMID: 33800476 PMCID: PMC7962950 DOI: 10.3390/ijms22052733] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/23/2021] [Accepted: 03/05/2021] [Indexed: 12/16/2022] Open
Abstract
Plants in the family Lemnaceae are aquatic monocots and the smallest, simplest, and fastest growing angiosperms. Their small size, the smallest family member is 0.5 mm and the largest is 2.0 cm, as well as their diverse morphologies make these plants ideal for laboratory studies. Their rapid growth rate is partially due to the family's neotenous lifestyle, where instead of maturing and producing flowers, the plants remain in a juvenile state and continuously bud asexually. Maturation and flowering in the wild are rare in most family members. To promote further research on these unique plants, we have optimized laboratory flowering protocols for 3 of the 5 genera: Spirodela; Lemna; and Wolffia in the Lemnaceae. Duckweeds were widely used in the past for research on flowering, hormone and amino acid biosynthesis, the photosynthetic apparatus, and phytoremediation due to their aqueous lifestyle and ease of aseptic culture. There is a recent renaissance in interest in growing these plants as non-lignified biomass sources for fuel production, and as a resource-efficient complete protein source. The genome sequences of several Lemnaceae family members have become available, providing a foundation for genetic improvement of these plants as crops. The protocols for maximizing flowering described herein are based on screens testing daylength, a variety of media, supplementation with salicylic acid or ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid) (EDDHA), as well as various culture vessels for effects on flowering of verified Lemnaceae strains available from the Rutgers Duckweed Stock Cooperative.
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Affiliation(s)
- Paul Fourounjian
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ 08854, USA
| | - Janet Slovin
- Genetic Improvement of Fruits & Vegetables Laboratory, USDA, Beltsville, MD 20705, USA;
| | - Joachim Messing
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ 08854, USA
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Oláh V, Hepp A, Gaibor Vaca NY, Tamás M, Mészáros I. Retrospective analyses of archive phytotoxicity test data can help in assessing internal dynamics and stability of growth in laboratory duckweed cultures. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2018; 201:40-46. [PMID: 29859406 DOI: 10.1016/j.aquatox.2018.05.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Revised: 05/18/2018] [Accepted: 05/27/2018] [Indexed: 06/08/2023]
Abstract
High growth potential of duckweed species (Lemnaceae family) has been utilized in wide range of research and practical applications. Based on literature data, however, it can be assumed that duckweed populations maintain constant growth rates only when short periods are considered but can vary over longer time scales. This intrinsic instability in growth can affect the interpretation of growth data. Duckweed phytotoxicity tests are usually performed according to highly standardized protocols. Therefore the archive data provide an opportunity for retrospective comparisons. In the present study we collected growth (frond number- and frond area-based relative growth rates) and morphology (average frond and colony sizes) data from control treatments of phytotoxicity tests. All the analyzed tests were carried out with the same Spirodela polyrhiza (L.) Schleid. (giant duckweed) clone (RDSC ID No. 5501) under the same experimental conditions over more than four years. We aimed to assess the overall variability of the above parameters and to test if intrinsic growth patterns affect growth data in short-term. In general, the results reflected high stability of the measured parameters in long term but also indicated that some temporal variability is inevitable which can bias the comparability of growth tests. The frond area-based relative growth rate resulted in smaller coefficient of variation than the usually preferred frond number-based one. The results also revealed a negative correlation between mean growth rates and their coefficients of variation. Therefore, it would be advisable to introduce higher minimal growth rates and/or maximized tolerable coefficients of variation for control cultures into the standard duckweed growth inhibition tests. Analyses of growth data aggregated on seasonal basis indicated faster growth and larger mean frond size in laboratory duckweed cultures from mid-autumn till mid-spring than during summer and early autumn. But, in shorter term (∼50 days) we did not observe distinct trends in growth suggesting that the successive frond generations have no effect on growth traits within this time-scale. Our results point to the importance of assessing intrinsic growth dynamics in duckweed cultures and also to the re-usability of the already collected phytotoxicity data in addressing new research questions.
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Affiliation(s)
- Viktor Oláh
- University of Debrecen, Faculty of Science and Technology, Department of Botany, Egyetem tér 1. Debrecen, Zip: H-4032, Hungary.
| | - Anna Hepp
- University of Debrecen, Faculty of Science and Technology, Department of Botany, Egyetem tér 1. Debrecen, Zip: H-4032, Hungary.
| | - Norma Yolanda Gaibor Vaca
- University of Debrecen, Faculty of Science and Technology, Department of Botany, Egyetem tér 1. Debrecen, Zip: H-4032, Hungary.
| | - Marianna Tamás
- University of Debrecen, Faculty of Science and Technology, Department of Botany, Egyetem tér 1. Debrecen, Zip: H-4032, Hungary.
| | - Ilona Mészáros
- University of Debrecen, Faculty of Science and Technology, Department of Botany, Egyetem tér 1. Debrecen, Zip: H-4032, Hungary.
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Beilby MJ, Turi CE, Baker TC, Tymm FJM, Murch SJ. Circadian changes in endogenous concentrations of indole-3-acetic acid, melatonin, serotonin, abscisic acid and jasmonic acid in Characeae (Chara australis Brown). PLANT SIGNALING & BEHAVIOR 2015; 10:e1082697. [PMID: 26382914 PMCID: PMC4883837 DOI: 10.1080/15592324.2015.1082697] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Giant-celled Characeae (Chara australis Brown), grown for 4 months on 12/12 hr day/night cycle and summer/autumn temperatures, exhibited distinct concentration maxima in auxin (indole-3-acetic acid; IAA), melatonin and serotonin about 4 hr after subjective daybreak. These concentration peaks persisted after 3 day pretreatment in continuous darkness: confirming a circadian rhythm, rather than a response to "light on." The plants pretreated for 3 d in continuous light exhibited several large IAA concentration maxima throughout the 24 hr. The melatonin and serotonin concentrations decreased and were less synchronized with IAA. Chara plants grown on 9/15 hr day/night cycle for 4 months and winter/spring temperatures contained much smaller concentrations of IAA, melatonin and serotonin. The IAA concentration maxima were observed in subjective dark phase. Serotonin concentration peaks were weakly correlated with those of IAA. Melatonin concentration was low and mostly independent of circadian cycle. The "dark" IAA concentration peaks persisted in plants treated for 3 d in the dark. The plants pretreated for 3 d in the light again developed more IAA concentration peaks. In this case the concentration maxima in melatonin and serotonin became more synchronous with those in IAA. The abscisic acid (ABA) and jasmonic acid (JA) concentrations were also measured in plants on winter regime. The ABA concentration did not exhibit circadian pattern, while JA concentration peaks were out of phase with those of IAA. The data are discussed in terms of crosstalk between metabolic pathways.
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Affiliation(s)
- Mary J Beilby
- School of Physics; University of NSW; Sydney, Australia
- Correspondence to: Mary J Beilby;
| | - Christina E Turi
- Department of Chemistry; University of British Columbia; Kelowna, Canada
| | - Teesha C Baker
- Department of Chemistry; University of British Columbia; Kelowna, Canada
| | - Fiona JM Tymm
- Department of Chemistry; University of British Columbia; Kelowna, Canada
| | - Susan J Murch
- Department of Chemistry; University of British Columbia; Kelowna, Canada
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Vunsh R, Heinig U, Malitsky S, Aharoni A, Avidov A, Lerner A, Edelman M. Manipulating duckweed through genome duplication. PLANT BIOLOGY (STUTTGART, GERMANY) 2015; 17 Suppl 1:115-119. [PMID: 25040392 DOI: 10.1111/plb.12212] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 04/19/2014] [Indexed: 06/03/2023]
Abstract
Significant inter- and intraspecific genetic variation exists in duckweed, thus the potential for genome plasticity and manipulation is high. Polyploidy is recognised as a major mechanism of adaptation and speciation in plants. We produced several genome-duplicated lines of Landoltia punctata (Spirodela oligorrhiza) from both whole plants and regenerating explants using a colchicine-based cocktail. These lines stably maintained an enlarged frond and root morphology. DNA ploidy levels determined by florescence-activated cell sorting indicated genome duplication. Line A4 was analysed after 75 biomass doublings. Frond area, fresh and dry weights, rhizoid number and length were significantly increased versus wild type, while the growth rate was unchanged. This resulted in accumulation of biomass 17-20% faster in the A4 plants. We sought to determine if specific differences in gene products are found in the genome duplicated lines. Non-targeted ultra performance LC-quadrupole time of flight mass spectrometry was employed to compare some of the lines and the wild type to seek identification of up-regulated metabolites. We putatively identified differential metabolites in Line A65 as caffeoyl hexoses. The combination of directed genome duplication and metabolic profiling might offer a path for producing stable gene expression, leading to altered production of secondary metabolites.
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Affiliation(s)
- R Vunsh
- Department of Plant Sciences, Weizmann Institute of Science, Rehovot, Israel
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7
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Abstract
Inherent characteristics of duckweed, including fast, clonal growth, small size and simple growth habit, argue for their use as a biomanufacturing platform for proteins, polymers and small molecules. This review addresses five areas relevant to commercialization of the duckweed platform: (1) the characteristics of wild-type duckweed and general cultural requirements; (2) the genetics and biochemistry of the plants and recent scientific developments that provide the technology necessary to genetically modify duckweed; (3) the advantages provided by inherent duckweed characteristics and genetic engineering technology relative to bioproduction; (4) recent progress towards commercialization of duckweed-based products and (5) the major research needs for further R&D.
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Affiliation(s)
- Anne-Marie Stomp
- Department of Forestry, North Carolina State University, Raleigh, NC 27695-8002, USA.
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8
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Ludwig-Müller J, Cohen JD. Identification and quantification of three active auxins in different tissues of Tropaeolum majus. PHYSIOLOGIA PLANTARUM 2002; 115:320-329. [PMID: 12060252 DOI: 10.1034/j.1399-3054.2002.1150220.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and phenylacetic acid (PAA) were identified as endogenous compounds with auxin activity in nasturtium (Tropaeolum majus L.) by full scan gas chromatography-mass spectrometry. The endogenous concentrations of the three auxins were measured by GC-selected ion monitoring-MS and isotope dilution analysis using stable labelled isotopes. PAA was present at concentrations about 10- to 100-fold lower than IAA, whereas IBA was found to be in the same concentration range as IAA. Free IAA was highest in roots followed by young leaves. IBA was also highest in the roots, and relatively high concentrations were found in young leaves and flowers. The distribution of PAA was quite different from that found for IBA. No PAA could be detected in young leaves and flowers, and in all other tissues studied the concentrations were well below those of the other two auxin compounds. The presence of a nitrilase gene family and nitrilase activity in extracts from T. majus suggests that PAA might be synthesized by the nitrilase pathway using benzylglucosinolate as precursor.
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Affiliation(s)
- Jutta Ludwig-Müller
- Institut für Botanik, Technische Universität Dresden, Zellescher Weg 22, D-01062, Dresden, Germany Department of Horticultural Science, University of Minnesota, 305 Alderman Hall, Saint Paul, MN 55108, USA
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Rapparini F, Tam YY, Cohen JD, Slovin JP. Indole-3-acetic acid metabolism in Lemna gibba undergoes dynamic changes in response to growth temperature. PLANT PHYSIOLOGY 2002; 128:1410-6. [PMID: 11950989 PMCID: PMC154268 DOI: 10.1104/pp.011005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2001] [Revised: 12/20/2001] [Accepted: 01/22/2002] [Indexed: 05/18/2023]
Abstract
Auxin is the mobile signal controlling the rate of growth and specific aspects of the development of plants. It has been known for over a century that auxins act as the messenger linking plant development to specific environmental changes. An often overlooked aspect of how this is accomplished is the effect of the environment on metabolism of the major plant auxin, indole-3-acetic acid (IAA). We have studied the metabolism of IAA in relation to one environmental variable, growth temperature. The model system used was an inbred line of the aquatic monocot Lemna gibba G-3, 3F7-11 grown at temperatures ranging from 5 degrees C to 35 degrees C. IAA levels, the rate of IAA turnover, and the patterns of label incorporation from IAA precursors were measured using stable isotope-mass spectrometric techniques and were evaluated relative to growth at the experimental temperatures. IAA levels exhibited unusually high variability in plants grown at 15 degrees C and 20 degrees C. Turnover rates were quite rapid throughout the range of experimental temperatures except at 25 degrees C, where IAA turnover was notably slower. These results suggest that a transition occurred over these temperatures for some aspect of IAA metabolism. Analysis of [(15)N]anthranilate and [(2)H(5)]tryptophan (Trp) incorporation into IAA showed that Trp-dependent biosynthesis predominated at 15 degrees C; however, Trp-independent biosynthesis of IAA was the major route to IAA at 30 degrees C. The effects of growth temperature on auxin levels have been reported previously, but no prior studies correlated these effects with which pathway becomes the primary one for IAA production.
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Affiliation(s)
- Francesca Rapparini
- Consiglio Nazionale della Ricerche, Istituto di Ecofisiologia delle Piante Arboree da Frutto, 40129 Bologna, Italy
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Jansen MA, van den Noort RE, Tan MY, Prinsen E, Lagrimini LM, Thorneley RN. Phenol-oxidizing peroxidases contribute to the protection of plants from ultraviolet radiation stress. PLANT PHYSIOLOGY 2001; 126:1012-23. [PMID: 11457952 PMCID: PMC116458 DOI: 10.1104/pp.126.3.1012] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2000] [Revised: 01/12/2001] [Accepted: 03/20/2001] [Indexed: 05/18/2023]
Abstract
We have studied the mechanism of UV protection in two duckweed species (Lemnaceae) by exploiting the UV sensitivity of photosystem II as an in situ sensor for radiation stress. A UV-tolerant Spirodela punctata G.F.W. Meyer ecotype had significantly higher indole-3-acetic acid (IAA) levels than a UV-sensitive ecotype. Parallel work on Lemna gibba mutants suggested that UV tolerance is linked to IAA degradation rather than to levels of free or conjugated IAA. This linkage is consistent with a role for class III phenolic peroxidases, which have been implicated both in the degradation of IAA and the cross-linking of various UV-absorbing phenolics. Biochemical analysis revealed increased activity of a specific peroxidase isozyme in both UV-tolerant duckweed lines. The hypothesis that peroxidases play a role in UV protection was tested in a direct manner using genetically modified tobacco (Nicotiana sylvestris). It was found that increased activity of the anionic peroxidase correlated with increased tolerance to UV radiation as well as decreased levels of free auxin. We conclude that phenol-oxidizing peroxidases concurrently contribute to UV protection as well as the control of leaf and plant architecture.
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Affiliation(s)
- M A Jansen
- Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom.
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Slovin JP, Bandurski RS, Cohen JD. Auxin. BIOCHEMISTRY AND MOLECULAR BIOLOGY OF PLANT HORMONES 1999. [DOI: 10.1016/s0167-7306(08)60485-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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12
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Delarue M, Prinsen E, Onckelen HV, Caboche M, Bellini C. Sur2 mutations of Arabidopsis thaliana define a new locus involved in the control of auxin homeostasis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1998; 14:603-11. [PMID: 9675903 DOI: 10.1046/j.1365-313x.1998.00163.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
A new auxin homeostasis gene in Arabidopsis called SUR2 has been identified. This gene, mapped to the bottom of chromosome 4, is defined by two recessive nuclear mutants designated superroot2 (sur2), which display several abnormalities reminiscent of auxin effects. A number of these characteristics are similar to the phenotype of the previously described auxin-overproducing mutant superroot1 (sur1); however, several lines of evidences reveal that the SUR2 gene defines a new key point in the regulation of endogenous auxin concentrations. The phenotype of the sur1 sur2 double mutant is additive. Analysis by gas chromatography coupled to mass spectrometry indicated increased levels of free indole-3-acetic acid correlated with a decreased level of bound auxin in the sur2 mutant. These results suggest that SUR2 may be involved in the control of auxin conjugation.
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Affiliation(s)
- M Delarue
- Laboratoire de Biologie Cellulaire, Versailles, France
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13
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Abstract
Indole-3-acetic acid (IAA) is the most abundant naturally occurring auxin. Plants produce active IAA both by de novo synthesis and by releasing IAA from conjugates. This review emphasizes recent genetic experiments and complementary biochemical analyses that are beginning to unravel the complexities of IAA biosynthesis in plants. Multiple pathways exist for de novo IAA synthesis in plants, and a number of plant enzymes can liberate IAA from conjugates. This multiplicity has contributed to the current situation in which no pathway of IAA biosynthesis in plants has been unequivocally established. Genetic and biochemical experiments have demonstrated both tryptophan-dependent and tryptophan-independent routes of IAA biosynthesis. The recent application of precise and sensitive methods for quantitation of IAA and its metabolites to plant mutants disrupted in various aspects of IAA regulation is beginning to elucidate the multiple pathways that control IAA levels in the plant.
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Affiliation(s)
- Bonnie Bartel
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005
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14
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Campanella JJ, Ludwig-Mueller J, Town CD. Isolation and characterization of mutants of Arabidopsis thaliana with increased resistance to growth inhibition by indoleacetic acid-amino acid conjugates. PLANT PHYSIOLOGY 1996; 112:735-45. [PMID: 8883385 PMCID: PMC157998 DOI: 10.1104/pp.112.2.735] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Two mutants of Arabidopsis thaliana that are resistant to growth inhibition by indole-3-acetic acid (IAA)-phenylalanine have been isolated. Both mutants were 2- to 3-fold more resistant than wild type to inhibition by IAA-phenylalanine, IAA-alanine, and IAA-glycine in root growth assays. The mutant icr1 (but not icr2) also shows some resistance to IAA-aspartate. Studies using 3H-labeled IAA-phenylalanine showed that the uptake of conjugate from the medium by icr1 was the same as wild type and was reduced by about 25% in icr2. No differences in hydrolysis of the exogenous conjugate were detected between the mutants and their wild-type parents. There was no significant metabolism of the IAA released from the [3H]IAA-phenylalanine, whereas exogenous [3H]IAA was rapidly metabolized to two unidentified products considerably more polar than IAA. Analysis of a cross between icr1 and icr2 indicated that these mutations were at distinct loci and that their effects were additive, and preliminary mapping data indicated that icr1 and icr2 were located at the top and bottom of chromosome V, respectively.
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Affiliation(s)
- J J Campanella
- Department of Biology, Case Western Reserve University, Cleveland, Ohio 44106, USA
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15
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King JJ, Stimart DP, Fisher RH, Bleecker AB. A Mutation Altering Auxin Homeostasis and Plant Morphology in Arabidopsis. THE PLANT CELL 1995; 7:2023-2037. [PMID: 12242367 PMCID: PMC161059 DOI: 10.1105/tpc.7.12.2023] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Many aspects of plant development are associated with changing concentrations of the phytohormone auxin. Several stages of root formation exhibit extreme sensitivities to exogenous auxin and are correlated with shifts in endogenous auxin concentration. In an effort to elucidate mechanisms regulating development of adventitious roots, an ethyl methanesulfonate-mutagenized M2 population of Arabidopsis was screened for mutants altered in this process. A recessive nuclear mutant, rooty (rty), displayed extreme proliferation of roots, inhibition of shoot growth, and other alterations suggesting elevated responses to auxin or ethylene. Wild-type Arabidopsis seedlings grown on auxin-containing media phenocopied rty, whereas rty seedlings were partially rescued on cytokinin-containing media. Analysis by gas chromatography-selected ion monitoring-mass spectrometry showed endogenous indole-3-acetic acid concentrations to be two to 17 times higher in rty than in the wild type. Dose-response assays with exogenous indole-3-acetic acid indicated equal sensitivities to auxin in tissues of the wild type and rty. Combining rty with mutations conferring resistance to auxin (axr1-3) or ethylene (etr1-1) suggested that root proliferation and restricted shoot growth are auxin effects, whereas other phenotypic alterations are due to ethylene. Four mutant alleles from independently mutagenized populations were identified, and the locus was mapped using morphological and restriction fragment length polymorphism markers to 3.9 centimorgans distal to marker m605 on chromosome 2. The wild-type RTY gene product may serve a critical role in regulating auxin concentrations and thereby facilitating normal plant growth and development.
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Affiliation(s)
- J. J. King
- Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706-1590
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Boerjan W, Cervera MT, Delarue M, Beeckman T, Dewitte W, Bellini C, Caboche M, Van Onckelen H, Van Montagu M, Inzé D. Superroot, a recessive mutation in Arabidopsis, confers auxin overproduction. THE PLANT CELL 1995; 7:1405-1419. [PMID: 8589625 DOI: 10.2307/3870131] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We have isolated seven allelic recessive Arabidopsis mutants, designated superroot (sur1-1 to sur1-7), displaying several abnormalities reminiscent of auxin effects. These characteristics include small and epinastic cotyledons, an elongated hypocotyl in which the connection between the stele and cortical and epidermal cells disintegrates, the development of excess adventitious and lateral roots, a reduced number of leaves, and the absence of an inflorescence. When germinated in the dark, sur1 mutants did not develop the apical hook characteristic of etiolated seedlings. We were able to phenocopy the Sur1- phenotype by supplying auxin to wild-type seedlings, to propagate sur1 explants on phytohormone-deficient medium, and to regenerate shoots from these explants by the addition of cytokinins alone to the culture medium. Analysis by gas chromatography coupled to mass spectrometry indicated increased levels of both free and conjugated indole-3-acetic acid. sur1 was crossed to the mutant axr2 and the altered-auxin response mutant ctr1. The phenotype of both double mutants was additive. The sur1 gene was mapped on chromosome 2 at 0.5 centimorgans from the gene encoding phytochrome B.
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Affiliation(s)
- W Boerjan
- Laboratorium voor Genetica, Universiteit Gent, Belgium
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Boerjan W, Cervera MT, Delarue M, Beeckman T, Dewitte W, Bellini C, Caboche M, Van Onckelen H, Van Montagu M, Inzé D. Superroot, a recessive mutation in Arabidopsis, confers auxin overproduction. THE PLANT CELL 1995; 7:1405-19. [PMID: 8589625 PMCID: PMC160963 DOI: 10.1105/tpc.7.9.1405] [Citation(s) in RCA: 200] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
We have isolated seven allelic recessive Arabidopsis mutants, designated superroot (sur1-1 to sur1-7), displaying several abnormalities reminiscent of auxin effects. These characteristics include small and epinastic cotyledons, an elongated hypocotyl in which the connection between the stele and cortical and epidermal cells disintegrates, the development of excess adventitious and lateral roots, a reduced number of leaves, and the absence of an inflorescence. When germinated in the dark, sur1 mutants did not develop the apical hook characteristic of etiolated seedlings. We were able to phenocopy the Sur1- phenotype by supplying auxin to wild-type seedlings, to propagate sur1 explants on phytohormone-deficient medium, and to regenerate shoots from these explants by the addition of cytokinins alone to the culture medium. Analysis by gas chromatography coupled to mass spectrometry indicated increased levels of both free and conjugated indole-3-acetic acid. sur1 was crossed to the mutant axr2 and the altered-auxin response mutant ctr1. The phenotype of both double mutants was additive. The sur1 gene was mapped on chromosome 2 at 0.5 centimorgans from the gene encoding phytochrome B.
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Affiliation(s)
- W Boerjan
- Laboratorium voor Genetica, Universiteit Gent, Belgium
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Tam YY, Slovin JP, Cohen JD. Selection and Characterization of [alpha]-Methyltryptophan-Resistant Lines of Lemna gibba Showing a Rapid Rate of Indole-3-Acetic Acid Turnover. PLANT PHYSIOLOGY 1995; 107:77-85. [PMID: 12228344 PMCID: PMC161170 DOI: 10.1104/pp.107.1.77] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Turnover rate is an important aspect of the regulation of plant processes by plant growth substances. To study turnover of indole-3-acetic acid (IAA), two [alpha]-methyltryptophan-resistant lines (MTR1 and MTR2) of Lemna gibba were generated by nitrosomethyl urea treatment of an inbred line derived from L. gibba G-3. In this report we describe: (a) the development of a selection system using this near isogenic line of L. gibba; (b) techniques for chemical mutation of the lines and selection for [alpha]-methyltryptophan resistance; and (c) the partial characterization of the selected lines. MTR lines contained 3-fold higher levels of anthranilate synthase activity. The enzyme in the MTR lines required higher levels of tryptophan for feedback inhibition. MTR lines also contained 8-fold higher levels of tryptophan, 3-fold higher levels of free IAA, and similar levels of total IAA compared to the inbred line. Turnover rates in the inbred and selected lines were calculated, using the first-order rate equation, based on the decrease over time in isotopic enrichment of I3C6-IAA introduced into L. gibba during a 1-h pulse period. Isotope enrichment in IAA was determined by using gas chromatography-mass spectrometry. Both MTR lines had an approximately 10-fold higher rate of IAA turnover than the parent inbred line.
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Affiliation(s)
- Y. Y. Tam
- Department of Botany, University of Maryland, College Park, Maryland 20742 (Y.Y.T.)
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Abstract
The effects of auxin on plant growth and development have been studied for decades, but the molecular mechanisms of auxin action remain unknown. These mechanisms have primarily been investigated by characterization of auxin physiology mutants and analysis of auxin-binding proteins and auxin-regulated genes. These efforts are now converging, since some mutants have recently been shown to have altered expression of specific auxin-binding proteins and auxin-regulated genes. The features of these proteins and genes are providing the first tantalizing clues to the organization of auxin signal transduction pathways.
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Affiliation(s)
- C Garbers
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
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Abstract
Answers to long-standing questions concerning the molecular mechanism of auxin action and auxin's exact functions in plant growth and development are beginning to be uncovered through studies using mutant and transgenic plants. We review recent work in this area in vascular plants. A number of conclusions can be drawn from these studies. First, auxin appears essential for cell division and viability, as auxin auxotrophs isolated in tissue culture are dependent on auxin for growth and cannot be regenerated into plants even when auxin is supplied exogenously. Secondly, plants with transgenes that alter auxin levels are able to regulate cellular auxin concentrations by synthesis and conjugation; wild-type plants are probably also capable of such regulation. Thirdly, the phenotypes of transgenic plants with altered auxin levels and of mutant plants with altered sensitivity to auxin confirm earlier physiological studies which indicated a role for auxin in regulation of apical dominance, in development of roots and vascular tissue, and in the gravitropic response. Finally, the cloning of a mutationally identified gene important for auxin action, along with accumulating biochemical evidence, hints at a major role for protein degradation in the auxin response pathway.
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Affiliation(s)
- L Hobbie
- Department of Biology, Indiana University, Bloomington 47405, USA
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Baldi BG, Maher BR, Slovin JP, Cohen JD. Stable Isotope Labeling, in Vivo, of d- and l-Tryptophan Pools in Lemna gibba and the Low Incorporation of Label into Indole-3-Acetic Acid. PLANT PHYSIOLOGY 1991; 95:1203-8. [PMID: 16668112 PMCID: PMC1077673 DOI: 10.1104/pp.95.4.1203] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
We present evidence that the role of tryptophan and other potential intermediates in the pathways that could lead to indole derivatives needs to be reexamined. Two lines of Lemna gibba were tested for uptake of [(15)N-indole]-labeled tryptophan isomers and incorporation of that label into free indole-3-acetic acid (IAA). Both lines required levels of l-[(15)N]tryptophan 2 to 3 orders of magnitude over endogenous levels in order to obtain measurable incorporation of label into IAA. Labeled l-tryptophan was extractable from plant tissue after feeding and showed no measurable isomerization into d-tryptophan. d-[(15)N]tryptophan supplied to Lemna at rates of approximately 400 times excess of endogenous d-tryptophan levels (to yield an isotopic enrichment equal to that which allowed detection of the incorporation of l-tryptophan into IAA), did not result in measurable incorporation of label into free IAA. These results demonstrate that l-tryptophan is a more direct precursor to IAA than the d isomer and suggest (a) that the availability of tryptophan in vivo is not a limiting factor in the biosynthesis of IAA, thus implying that other regulatory mechanisms are in operation and (b) that l-tryptophan also may not be a primary precursor to IAA in plants.
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Affiliation(s)
- B G Baldi
- U.S. Department of Agriculture, Agricultural Research Service, Plant Hormone Laboratory, Product Quality and Development Institute, Beltsville Agricultural Research Center, Beltsville, Maryland 20705
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Oetiker J, Gebhardt C, King PJ. A temperature-sensitive auxin auxotroph not deficient in indole-3-acetic acid. PLANTA 1990; 180:220-228. [PMID: 24201949 DOI: 10.1007/bf00194000] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/1989] [Accepted: 07/03/1989] [Indexed: 06/02/2023]
Abstract
A temperature-sensitive variant of Hyoscyamus muticus L. expressing a lethal phenotype in both cultured cells and regenerated plants has been shown to be a conditional auxin auxotroph with an absolute requirement for an exogenous auxin at temperatures above 30° C but not at lower temperatures. The requirement was satisfied by indole-3-acetic acid (IAA) and all active auxin analogous tested. Despite this dependence on exogenous auxin at high temperatures, the variant nevertheless synthesises IAA under these conditions and contains a pool of free IAA equal to that of the wild type. Furthermore, there is no depletion of the cellular IAA pool on incubation at high temperature in the absence of added auxin, even during the expression of the auxin-auxotrophic phenotype. The characteristics of this variant indicate that auxin auxotrophy can be lethal at the plant level and raises questions about the cellular function and mode of action of auxin.
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Affiliation(s)
- J Oetiker
- Friedrich Miescher-Institut, Postfach 2543, CH-4002, Basel, Switzerland
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