Polar auxin transport: controlling where and how much

Muday, Gloria K.; DeLong, Alison

doi:10.1016/s1360-1385(01)02101-x

Cited by 243 publications

(180 citation statements)

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“…3-5). Furthermore, this increase in IAA in the cotyledons can be significantly decreased or delayed by (1) excision of the shoot; (2) growth in the darkness; and (3) use of NPA, an inhibitor of polar auxin transport (Jensen et al, 1998;Reed et al, 1998;Muday and DeLong, 2001). As the addition of 10 26 M 2,4-D to detached cotyledons was able to induce an increase in xyloglucan degradation, starch biosynthesis and at the same time promote xyloglucan hydrolase activities, it can also be deduced that these events are possibly under the control of auxin, as has been observed for primary (Hoson, 1993;Valero and Labrador, 1995;Catalá et al, 1997Catalá et al, , 2000Kotake et al, 2000) and storage cell walls (Hensel et al, 1991).…”

Section: Auxin and Xyloglucan Mobilizationmentioning

confidence: 99%

The Control of Storage Xyloglucan Mobilization in Cotyledons of Hymenaea courbaril

et al. 2004

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Hymenaea courbaril is a leguminous tree species from the neotropical rain forests. Its cotyledons are largely enriched with a storage cell wall polysaccharide (xyloglucan). Studies of cell wall storage polymers have been focused mostly on the mechanisms of their disassembly, whereas the control of their mobilization and the relationship between their metabolism and seedling development is not well understood. Here, we show that xyloglucan mobilization is strictly controlled by the development of first leaves of the seedling, with the start of its degradation occurring after the beginning of eophyll (first leaves) expansion. During the period of storage mobilization, an increase in the levels of xyloglucan hydrolases, starch, and free sugars were observed in the cotyledons. Xyloglucan mobilization was inhibited by shoot excision, darkness, and by treatment with the auxin-transport inhibitor N-1-naphthylphthalamic acid. Analyses of endogenous indole-3-acetic acid in the cotyledons revealed that its increase in concentration is followed by the rise in xyloglucan hydrolase activities, indicating that auxin is directly related to xyloglucan mobilization. Cotyledons detached during xyloglucan mobilization and treated with 2,4-dichlorophenoxyacetic acid showed a similar mobilization rate as in attached cotyledons. This hormonal control is probably essential for the ecophysiological performance of this species in their natural environment since it is the main factor responsible for promoting synchronism between shoot growth and reserve degradation. This is likely to increase the efficiency of carbon reserves utilization by the growing seedling in the understorey light conditions of the rain forest.

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Section: Auxin and Xyloglucan Mobilizationmentioning

confidence: 99%

The Control of Storage Xyloglucan Mobilization in Cotyledons of Hymenaea courbaril

et al. 2004

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“…The powerful tools of molecular biology and genetics, and the availability of the complete genome sequence have made Arabidopsis thaliana the model organism of choice in plant biology, and there is currently a renewed interest in elucidating the biosynthesis, metabolism and transport of IAA in this species (for reviews : Eckhardt 2001;and Muday and DeLong 2001).…”

Section: Introductionmentioning

confidence: 99%

Occurrence and formation of indole-3-acetamide in Arabidopsis thaliana

Pollmann

Müller

Piotrowski

et al. 2002

Planta

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An HPLC/GC-MS/MS technique (high-pressure liquid chromatography in combination with gas chromatography-tandem mass spectrometry) has been worked out to analyze indole-3-acetamide (IAM) with very high sensitivity, using isotopically labelled IAM as an internal standard. Using this technique, the occurrence of IAM in sterile-grown Arabidopsis thaliana (L.) Heynh. was demonstrated unequivocally. In comparison, plants grown under non-sterile conditions in soil in a greenhouse showed approximately 50% higher average levéis of IAM, but the differences were not statistically significant. Thus, microbial contributions to the IAM extracted from the tissue are likely to be minor. Levéis of IAM in sterile-grown seedlings were highest in imbibed seeds and then sharply declined during the first 24 h of germination and further during early seedling development to remain below 20-30 pmol g l fresh weight throughout the rosette stage. The decline in indole-3-aetic acid (IAA) levéis during germination was paralleled by a similar decline in IAM levéis. Recombinant nitrilase isoforms 1, 2 and 3, known to synthesize IAA from indole-3-acetonitrile, were shown to produce significant amounts of IAM in vitro as a second end product of the reaction besides IAA. NIT2 was earlier shown to be highly expressed in developing and in matare A. thaliana embryos, and NIT3 is the dominantly active gene in the hypocotyl and the cotyledons of young, germinating seedlings. Collectively, these data suggest that the elevated levéis of IAM in seeds and germinating seedlings result from nitrilase action on indole-3-acetonitrile, a metabolite produced in the plants presumably from glucobrassicin turnover.

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“…Savidge, 2001). Nevertheless, it is possible that the plant hormone auxin may be involved in this process, because a number of studies have provided evidence for a role of this hormone in different aspects of vascular tissue development (for review, see Sachs, 1981; Berleth et al, 2000).One key feature of auxin action is its translocation from cell to cell in a polar fashion, a process that is referred to as polar auxin transport (PAT; Goldsmith, 1977;Lomax et al, 1995;Muday and DeLong, 2001;Muday and Murphy, 2002). In the shoot, auxin moves unidirectionally through the vascular tissues from the apex to the base.…”

mentioning

confidence: 99%

“…One key feature of auxin action is its translocation from cell to cell in a polar fashion, a process that is referred to as polar auxin transport (PAT; Goldsmith, 1977;Lomax et al, 1995;Muday and DeLong, 2001;Muday and Murphy, 2002). In the shoot, auxin moves unidirectionally through the vascular tissues from the apex to the base.…”

mentioning

confidence: 99%

“…Auxin entry into cells is facilitated by an auxin influx carrier that is thought to be encoded by AUX1 (Marchant et al, 1999) and possibly by related genes (Parry et al, 2001). Auxin moves out of plant cells through an efflux carrier apparatus that is sensitive to synthetic PAT inhibitors (PATIs), such as 1-N-naphthylphthalamic acid (NPA), and requires the activity of at least two polypeptides (Morris, 2000;Muday and DeLong, 2001;Muday and Murphy, 2002). The first is an integral membrane transporter thought to be encoded by one of the members of the PIN gene family (Palme and Gäl-weiler, 1999).…”

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confidence: 99%

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The Procambium Specification Gene Oshox1 Promotes Polar Auxin Transport Capacity and Reduces Its Sensitivity toward Inhibition

et al. 2002

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The auxin-inducible homeobox gene Oshox1 of rice (Oryza sativa) is a positive regulator of procambial cell fate commitment, and its overexpression reduces the sensitivity of polar auxin transport (PAT) to the PAT inhibitor 1-N-naphthylphthalamic acid (NPA). Here, we show that wild-type rice leaves formed under conditions of PAT inhibition display vein hypertrophy, reduced distance between longitudinal veins, and increased distance between transverse veins, providing experimental evidence for a role of PAT in vascular patterning in a monocot species. Furthermore, we show that Oshox1 overexpression confers insensitivity to these PAT inhibitor-induced vascular-patterning defects. Finally, we show that in the absence of any overt phenotypical change, Oshox1 overexpression specifically reduces the affinity of the NPA-binding protein toward NPA and enhances PAT and its sensitivity toward auxin. These results are consistent with the hypothesis that Oshox1 promotes fate commitment of procambial cells by increasing their auxin conductivity properties and stabilizing this state against modulations of PAT by an endogenous NPA-like molecule.During development of multicellular organisms, most cells enter specific differentiation programs that overtly change their structure and specialize them toward a distinct function. Cell differentiation is preceded by the process of cell fate commitment, in which the developmental potential of the cell becomes restricted to a certain fate or subset of fates, but the explicit demonstration and realization of that developmental pathway is not yet apparent (Maclean and Hall, 1987). Cell fate commitment has been divided into the processes of specification and determination (Slack, 1991). However, the definitions of these processes are, by nature, operational, and knowledge of the molecular nature underlying the effective functional properties of specified or determined cell states in plants is still mostly lacking.The vascular tissues of plants represent an attractive system for the study of cell fate commitment. In fact, vascular tissues consist of several distinct cell types arranged in a network of continuous strands to form a system of exquisitely complex topography (Steeves and Sussex, 1989). Yet, all types of highly specialized vascular cells derive from an anatomically homogeneous population of meristematic cells, the procambium, or provascular tissue. We have previously developed assays with which different stages of procambial cell fate commitment in rice (Oryza sativa) could be distinguished (Scarpella et al., 2000). However, despite the detailed studies available on different aspects of vascular development (for review, see Sachs, 1981Sachs, , 2000Fukuda, 1996Fukuda, , 1997Nelson and Dengler, 1997; Berleth et al., 2000; Aloni, 2001; Dengler, 2001; Dengler and Kang, 2001;Kuriyama and Fukuda, 2001;Ye, 2002), the molecular mechanisms underlying procambial cell fate commitment remain elusive (e.g. Savidge, 2001). Nevertheless, it is possible that the plant hormone auxin may be involv...

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Polar auxin transport: controlling where and how much

Cited by 243 publications

References 57 publications

The Control of Storage Xyloglucan Mobilization in Cotyledons of Hymenaea courbaril

The Control of Storage Xyloglucan Mobilization in Cotyledons of Hymenaea courbaril

Occurrence and formation of indole-3-acetamide in Arabidopsis thaliana

The Procambium Specification Gene Oshox1 Promotes Polar Auxin Transport Capacity and Reduces Its Sensitivity toward Inhibition

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