Plant hormone mutants

King, Patrick J.

doi:10.1016/0168-9525(88)90021-2

Cited by 52 publications

(16 citation statements)

References 11 publications

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“…Bowman and E.M. Meyerowitz, unpublished data). The second is that there are Arabidopsis mutants known that either fail to produce, or fail to respond properly to gibberellins, auxins, abscisic acid, and ethylene; none of these mutations give phenotypes involving homeotic conversions (Koornneef et al, 1985;Bleecker et al, 1988;King, 1988).…”

Section: Discussionmentioning

confidence: 99%

Genes directing flower development in Arabidopsis.

1989

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We describe the effects of four recessive homeotic mutations that specifically disrupt the development of flowers in Arabidopsis thaliana. Each of the recessive mutations affects the outcome of organ development, but not the location of organ primordia. Homeotic transformations observed are as follows. In agamous-1, stamens to petals; in apetala2-1, sepals to leaves and petals to staminoid petals; in apefala3-1, petals to sepals and stamens to carpels; in pistillata-1, petals to sepals. In addition, two of these mutations (ap2-1 and pi-1) result in loss of organs, and ag-1 causes the cells that would ordinarily form the gynoecium to differentiate as a flower. Two of the mutations are temperature-sensitive. Temperature shift experiments indicate that the wild-type AP2 gene product acts at the time of primordium initiation; the AP3 product is active later. It seems that the wild-type alleles of these four genes allow cells to determine their place in the developing flower and thus to differentiate appropriately. We propose that these genes may be involved in setting up or responding to concentric, overlapping fields within the flower primordium.

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Section: Discussionmentioning

confidence: 99%

Genes directing flower development in Arabidopsis.

1989

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“…Cytokinins are believed to play regulatory roles in two processes that describe plant development: growth and differentiation (Finkelstein et al, 1987;King, 1988). Elucidation of processes that cytokinins affect has come, in part, from studies where the hormone is applied externally.…”

Section: Discussionmentioning

confidence: 99%

Alterations of Endogenous Cytokinins in Transgenic Plants Using a Chimeric Isopentenyl Transferase Gene.

et al. 1989

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Cytokinins, a class of phytohormones, appear to play an important role in the processes of plant development. We genetically engineered the Agrobacterium tumefaciens isopentenyl transferase gene, placing it under control of a heat-inducible promoter (maize hsp70). The chimeric hsp7O isopentenyl transferase gene was transferred to tobacco and Arabidopsis plants. Heat induction of transgenic plants caused the isopentenyl transferase mRNA to accumulate and increased the level of zeatin 52-fold, zeatin riboside 23-fold, and zeatin riboside 5'-monophosphate twofold. At the control temperature zeatin riboside and zeatin riboside 5'-monophosphate in transgenic plants accumulated to levels 3 and 7 times, respectively, over levels in wild-type plants. This uninduced cytokinin increase affected various aspects of development. In tobacco, these effects included release of axillary buds, reduced stem and leaf area, and an underdeveloped root system. In Arabidopsis, reduction of root growth was also found. However, neither tobacco nor Arabidopsis transgenic plants showed any differences relative to wild-type plants in time of flowering. Unexpectedly, heat induction of cytokinins in transgenic plants produced no changes beyond those seen in the uninduced state. The lack of effect from heat-induced increases could be a result of the transient increases in cytokinin levels, direct or indirect induction of negating factor(s), or lack of a corresponding level of competent cellular factors. Overall, the effects of the increased levels of endogenous cytokinins in non-heat-shocked transgenic plants seemed to be confined to aspects of growth rather than differentiation. Since no alterations in the programmed differentiation pattern were found with increased cytokinin levels, this process may be controlled by components other than absolute cytokinin levels.

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“…Although no mutants clearly blocked in auxin biosynthesis have been described (King, 1988;Reid, 19931, other classes of putative IAA mutants have been found in several plants. Examples include the jsR1 mutant in Lemna (Slovin and Cohen, 1988), a series of trp mutants in Arabidopsis (see Normanly et al, 1993), and the orp mutants of maize (Wright et al, 1991).…”

Section: Iaa Metabolismmentioning

confidence: 99%

Selection and Characterization of [alpha]-Methyltryptophan-Resistant Lines of Lemna gibba Showing a Rapid Rate of Indole-3-Acetic Acid Turnover

1995

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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 a-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 a-methyltryptophan resistance; and (c) the partia1 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 13C,-IAA introduced into L. gibba during a 1-h pulse period. lsotope 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 lhe.IAA plays an important role in plant growth, development, and responses to the environment, yet after more than a century of study we still have large gaps in our knowledge of fundamental aspects of how the hormone acts and what controls its metabolism. One aspect of plant hormone metabolism that has attracted attention over the last 15 years is the rate of hormone turnover (Epstein et al., 1980;Nonhebel and Cooney, 1990). Hormonal homeostasis requires that increased rates of synthesis of IAA be offset by increasing rates of degradation, resulting in more rapid turnover. Studies of hormone turnover have been limited in number in part by lack of plant systems that overcome the difficulties of labeling interna1 pools. In many cases, IAA levels in plant tissues remain relatively constant, but changes in the rates of IAA biosynthesis and degradation are seen only as changes in turnover rate. To date we have information on turnover in only a few plants and no knowledge of how turnover might change relative to genetic, developmental, and environmental variation. Turnover can be expected to be an important metabolic parameter for hormone action, since rates of turnover must be rapid relative to the processes that are controlled by the particular hormone (see Cohen, 1983). A mechanism linking turnover and hormone action may involve the co-oxidation of plant fatty acids (Reineke, 1990).Studies of IAA biosynthesis have shown the utility of using mutants to study IAA and Trp metabolism (Wright et al., 1991;Normanly et al., 1993). Unlike mutants used for studies of metabolic pathways, those most useful for understanding the function of IAA turnover would not be auxotrophs, but rather would be modified in metabolism so as to result in...

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Plant hormone mutants

Cited by 52 publications

References 11 publications

Genes directing flower development in Arabidopsis.

Genes directing flower development in Arabidopsis.

Alterations of Endogenous Cytokinins in Transgenic Plants Using a Chimeric Isopentenyl Transferase Gene.

Selection and Characterization of [alpha]-Methyltryptophan-Resistant Lines of Lemna gibba Showing a Rapid Rate of Indole-3-Acetic Acid Turnover

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