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Liscum, Emmanuel; Reed, Jason W.

doi:10.1023/a:1015255030047

Cited by 613 publications

(234 citation statements)

References 84 publications

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“…1C) is not sufficient to stimulate expression of all auxin-responsive genes. For example, At2g23170͞GH3.3 (21) and AT4G14550͞SLR͞IAA14 (25), although expressed in B. oleracea hypocotyls segments, did not exhibit differential expression in response to tropic stimulation (Fig. 3).…”

Section: Tsi Transcript Accumulation Depends Upon Auxin and Occurs Comentioning

confidence: 95%

A gradient of auxin and auxin-dependent transcription precedes tropic growth responses

Esmon

Tinsley

Ljung

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

210

218

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Yet the molecular identities of such output components, which are likely to encode proteins directly involved in growth control, have remained elusive. Here we report the discovery of a suite of tropic stimulus-induced genes in Brassica oleracea that are responsive to an auxin gradient and exhibit morphologically graded expression concomitant with, or before, observable curvature responses. These results provide compelling molecular support for the Cholodny-Went theory and suggest that morphologically graded transcription represents an important mechanism for interpreting tropically stimulated gradients of auxin. Intriguingly, two of the tropic stimulus-induced genes, EXPA1 and EXPA8, encode enzymes involved in cell wall extension, a response prerequisite for differential growth leading to curvatures, and are up-regulated before curvature in the flank that will elongate. This observation suggests that morphologically graded transcription likely leads to the graded expression of proteins whose activities can directly regulate the establishment and modulation of tropic curvatures.gravitropism ͉ NPH4͞ARF7 ͉ phototropism

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Section: Tsi Transcript Accumulation Depends Upon Auxin and Occurs Comentioning

confidence: 95%

A gradient of auxin and auxin-dependent transcription precedes tropic growth responses

Esmon

Tinsley

Ljung

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

210

218

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“…Another LEC2-induced RNA, IAA30, encodes one of a family of auxin signaling proteins (48) that is enriched in the quiescent center of Arabidopsis root apical meristems (49). Thus, IAA30 may play one of two distinct roles in the induction of somatic embryogenesis.…”

Section: Lec2 Directly Activates Genes Involved In Maturation Processesmentioning

confidence: 99%

Genes directly regulated by LEAFY COTYLEDON2 provide insight into the control of embryo maturation and somatic embryogenesis

Braybrook

Stone

Park

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

324

331

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The B3 domain protein LEAFY COTYLEDON2 (LEC2) is required for several aspects of embryogenesis, including the maturation phase, and is sufficient to induce somatic embryo development in vegetative cells. Here, we demonstrate that LEC2 directly controls a transcriptional program involved in the maturation phase of seed development. Induction of LEC2 activity in seedlings causes rapid accumulation of RNAs normally present primarily during the maturation phase. Several RNAs encode proteins with known roles in maturation processes, including seed-storage and lipid-body proteins. Clustering analyses identified other LEC2-induced RNAs not previously shown to be involved in the maturation phase. We show further that genes encoding these maturation RNAs all possess in their 5 flanking regions RY motifs, DNA elements bound by other closely related B3 domain transcription factors. Our finding that recombinant LEC2 specifically binds RY motifs from the 5 flanking regions of LEC2-induced genes provides strong evidence that these genes represent transcriptional targets of LEC2. Although these LEC2-induced RNAs accumulate primarily during the maturation phase, we show that a subset, including AGL15 and IAA30, accumulate in seeds containing zygotes. We discuss how identification of LEC2 target genes provides a potential link between the roles of LEC2 in the maturation phase and in the induction of somatic embryogenesis.Arabidopsis ͉ B3 domain E mbryogenesis in higher plants can be divided conceptually into two distinct phases. Early in embryogenesis, during the morphogenesis phase, the basic body plan of the plant is established with regional specification of apical-basal and radial domains from which morphological structures derive, fixation of polarity from specification of the shoot-root axis, and formation of embryonic tissue and organ systems (1-3). The morphogenesis phase is followed temporally by the maturation phase, although the two phases can overlap (4, 5). During the maturation phase, embryo cell-division rates decline markedly, embryo cells acquire the ability to withstand desiccation, and embryo cell growth occurs, with the accumulation of storage reserves that comprise lipids and proteins in Arabidopsis (6, 7). At the end of the maturation phase, the embryo becomes quiescent metabolically as the seed desiccates.The maturation phase can be viewed as an interruption of an ancestral life cycle, as occurs in lower plants, in which there are no periods of maturation or dormancy separating the end of embryogenesis and the beginning of postembryonic development (4). Evolution of this unique mode of embryogenesis has enabled higher plants to make seeds. The ability to make seeds has provided tremendous selective advantages that, in part, account for the success of the angiosperms (8, 9). Little is known at a mechanistic level about the processes by which the maturation phase has been integrated into the higher plant life cycle. LEAFY COTYLEDON2 (LEC2), along with ABA INSEN-SITIVE3 (ABI3), and FUSCA3 (FUS3), have been im...

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“…Low concentrations of YkB stimulate lateral roots, whereas higher concentrations inhibit root formation. Similarly, the phenotype of axr1-12, tir1, iaa14/slr1, iaa19/msg2, iaa28, and iaa6/shy1 have fewer lateral roots, whereas iaa7/axr2-1 and iaa17/axr3 have more lateral roots than wild type (3,8). Stabilization of individual AUX/IAA proteins with these dominant mutations confers distinct repression profiles in primary auxin-responsive genes, which is presumably the basis for the different phenotypes among mutants (i.e.…”

Section: Ykb Acts On Upstream Components Of Axr1 and Tir1-ifmentioning

confidence: 99%

“…Consistent with the diverse effects of auxin on growth and development is that the expression patterns of a number of genes are dramatically and rapidly altered by auxin application (2), suggesting that auxin ultimately regulates cell growth by controlling the profile of expressed genes. AUX/IAA genes comprise a 34-member gene family in Arabidopsis that is one of three known gene families that are regulated by auxin and implicated to play essential roles in auxin signaling (3,4).…”

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confidence: 99%

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Yokonolide B, a Novel Inhibitor of Auxin Action, Blocks Degradation of AUX/IAA Factors

Hayashi

Jones

Ogino

et al. 2003

Journal of Biological Chemistry

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Yokonolide B (YkB; also known as A82548A), a spiroketal-macrolide, was isolated from Streptomyces diastatochromogenes B59 in a screen for inhibitors of ␤-glucoronidase expression under the control of an auxin-responsive promoter in Arabidopsis. YkB inhibits the expression of auxin-inducible genes as shown using native and synthetic auxin promoters as well as using expression profiling of 8,300 Arabidopsis gene probes but does not affect expression of an abscisic acid-and a gibberellin A 3 -inducible gene. The mechanism of action of YkB is to block AUX/IAA protein degradation; however, YkB is not a general proteasome inhibitor. YkB blocks auxin-dependent cell division and auxin-regulated epinastic growth mediated by auxin-binding protein 1. Gain of function mutants such as shy2-2, slr1, and axr2-1 encoding AUX/IAA transcriptional repressors and loss of function mutants encoding components of the ubiquitin-proteolytic pathway such as axr1-3 and tir1-1, which display increased AUX/IAAs protein stability, are less sensitive to YkB, although axr1 and tir1 mutants were sensitive to MG132, a general proteasome inhibitor, consistent with a site of action downstream of AXR1 and TIR. YkB-treated seedlings displayed similar phenotypes as dominant AUX/IAA mutants. Taken together, these results indicate that YkB acts to block AUX/IAA protein degradation upstream of AXR and TIR, links a shared element upstream of AUX/IAA protein stability to auxin-induced cell division/elongation and to auxin-binding protein 1, and provides a new tool to dissect auxin signal transduction.Auxin controls cell division, elongation, and differentiation and therefore, through its action at the level of the cell, exerts profound effects on growth and development throughout the life of the plant (1). Consistent with the diverse effects of auxin on growth and development is that the expression patterns of a number of genes are dramatically and rapidly altered by auxin application (2), suggesting that auxin ultimately regulates cell growth by controlling the profile of expressed genes. AUX/IAA genes comprise a 34-member gene family in Arabidopsis that is one of three known gene families that are regulated by auxin and implicated to play essential roles in auxin signaling (3, 4).The molecular and genetic studies on auxin signaling have revealed that auxin specifically enhances the transcription of many AUX/IAA genes within minutes without requiring de novo protein synthesis, suggesting that AUX/IAA genes are primary auxin-response genes (5, 6). AUX/IAA genes encode short lived nuclear proteins capable of heterodimerization with auxin-responsive factors (7) and are thought to act by negatively regulating the expression of early auxin-responsive genes including other members of the AUX/IAA family (3).Studies on Arabidopsis mutants with altered responses to auxin such as iaa3/shy2-2, iaa7/axr2-1, iaa17/axr3, iaa14/slr1, tir1, and axr1 revealed that the turnover rate of AUX/IAA proteins is in some way important in various developmental processes including ...

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Untitled

Cited by 613 publications

References 84 publications

A gradient of auxin and auxin-dependent transcription precedes tropic growth responses

A gradient of auxin and auxin-dependent transcription precedes tropic growth responses

Genes directly regulated by LEAFY COTYLEDON2 provide insight into the control of embryo maturation and somatic embryogenesis

Yokonolide B, a Novel Inhibitor of Auxin Action, Blocks Degradation of AUX/IAA Factors

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