Translocation in Legumes: Assimilates, Nutrients, and Signaling Molecules1

Atkins, Craig A.; Smith, Penelope M. C.

doi:10.1104/pp.107.098046

Cited by 63 publications

(42 citation statements)

References 124 publications

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“…Upon initiation of Pi deficiency, roots first sense the changes and emit two types of response: one is the local response restricted to the roots directly exposed to the nutrient; the other is a systemic response of sending a signal to shoots (Forde, 2002;Atkins and Smith, 2007;Schachtman and Shin, 2007). A systemic root-born signal is delivered through the xylem to trigger the initial expression of miR399s in shoots (Fig.…”

Section: Biological Relevance Of the Movement Of Mir399mentioning

confidence: 99%

“…Hormones and nutrients themselves or their derivates could be potential candidates of long-distance signals (Forde, 2002;Atkins and Smith, 2007;Schachtman and Shin, 2007). In the case of phosphorus, Pi itself does not appear to be a long-distance signal from shoots; instead, allocation or recycling of Pi between shoots and roots is considered to provide the systemic signals (Drew and Saker, 1984;Jeschke et al, 1997;Burleigh and Harrison, 1999).…”

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confidence: 99%

“…Therefore, communication between roots and shoots is indispensable; longdistance signals are required to report the nutrient status in these tissues. Local and long-distance signaling pathways are triggered when the nutrient concentration fluctuates (Forde, 2002;Atkins and Smith, 2007;Schachtman and Shin, 2007). The local signaling pathway is restricted to roots directly exposed to nutrient solutions, such as in the localized proliferation of branch roots and root hairs in response to the availability of nitrate, inorganic phosphate (Pi), and iron (Robinson, 1994;Bates and Lynch, 1996;Schikora and Schmidt, 2001).…”

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Regulatory Network of MicroRNA399 andPHO2by Systemic Signaling

et al. 2008

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Recently, we showed that microRNA399s (miR399s) control inorganic phosphate (Pi) homeostasis by regulating the expression of PHO2 encoding a ubiquitin-conjugating E2 enzyme 24. Arabidopsis (Arabidopsis thaliana) plants overexpressing miR399 or the pho2 mutant overaccumulate Pi in shoots. The association of Pi translocation and coexpression of miR399s and PHO2 in vascular tissues suggests their involvement in long-distance signaling. In this study, we used reciprocal grafting between wild-type and miR399-overexpressing transgenic plants to dissect the systemic roles of miR399 and PHO2. Arabidopsis rootstocks overexpressing miR399 showed high accumulation of Pi in the wild-type scions because of reduced PHO2 expression in the rootstocks. Although miR399 precursors or expression was not detected, we found a small but substantial amount of mature miR399 in the wild-type rootstocks grafted with transgenic scions, which indicates the movement of miR399 from shoots to roots. Suppression of PHO2 with miR399b or c was less efficient than that with miR399f. Of note, findings in grafted Arabidopsis were also discovered in grafted tobacco (Nicotiana benthamiana) plants. The analysis of the pho1 mutant provides additional support for systemic suppression of PHO2 by the movement of miR399 from Pi-depleted shoots to Pi-sufficient roots. We propose that the long-distance movement of miR399s from shoots to roots is crucial to enhance Pi uptake and translocation during the onset of Pi deficiency. Moreover, PHO2 small interfering RNAs mediated by the cleavage of miR399s may function to refine the suppression of PHO2. The regulation of miR399 and PHO2 via long-distance communication in response to Pi deficiency is discussed.

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Section: Biological Relevance Of the Movement Of Mir399mentioning

confidence: 99%

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confidence: 99%

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Regulatory Network of MicroRNA399 andPHO2by Systemic Signaling

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“…Root-shoot communication likely follows either the internal vascular network of the plant (i.e. phloem and xylem bundles; Orians, 2005;Atkins and Smith, 2007) or the external route via volatile signaling. These possible routes and preferential flows are depicted in Figure 1.…”

Section: The Physiological Basis Of Root-shoot Interactionsmentioning

confidence: 99%

Interactions between Arthropod-Induced Aboveground and Belowground Defenses in Plants

et al. 2008

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Plants can be attacked by arthropods both above and below ground. The ensuing systemic defense response of the plant can affect even the most distant tissues. Both primary and secondary metabolic profiles of shoots can be altered upon root herbivory and vice versa (Gange and Brown, 1989;Bezemer et al., 2003;Hol et al., 2004;Schwachtje et al., 2006), making plants powerful mediators of interactions between otherwise loosely connected food webs Bardgett and Wardle, 2003). Whereas the ecological relevance of such processes has been recognized and the role of primary and secondary metabolites acknowledged (for review, see Blossey and Hunt-Joshi, 2003;van Dam et al., 2003;Bezemer and van Dam, 2005), it remains to be explored exactly how plants coordinate their root and shoot responses against herbivores.We propose that results from current research into the mechanisms governing plant stress responses might provide several starting points to explore the physiological basis of plant-mediated aboveground and belowground interactions. Priming (Ryals et al., 1996;van Wees et al., 1999;Ton et al., 2005;Conrath et al., 2006;Frost et al., 2008) and plant volatile signaling (Engelberth et al., 2004;Heil and Kost, 2006;Ton et al., 2007) may be particularly relevant, and we attempt to place these novel insights in the context of interactions between aboveground and belowground plant defense responses.Because of the scope of this Focus Issue, we limit our review to arthropod-induced plant defense responses. We do not discuss induced changes in primary metabolites, which can be of substantial importance (Mattson, 1980;Gange and Brown, 1989;Babst et al., 2005;Schwachtje et al., 2006;Schwachtje and Baldwin, 2008). We also acknowledge the importance of putting the current findings in an appropriate ecological context (Rasmann and Agrawal, 2008) and the necessity of including microorganisms as important players in both rhizosphere and phyllosphere interactions. Several excellent reviews cover these and other intricacies of aboveground and belowground interactions (van der Putten et al

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“…How hormones are translocated from their site of origin to other plant parts will likely play a key role in shoot-to-root communication (Atkins and Smith, 2007). Some signaling molecules follow phloem ducts to reach root cells (Sachs, 2005), but how a damaged root alerts the leaves to mobilize or synthesize defensive compounds still remains unclear.…”

Section: Signaling Pathways Of Plant Defense Induction Undergroundmentioning

confidence: 99%