Enhancement of Phloem Exudation from <i>Fraxinus uhdei</i> Wenz. (Evergreen Ash) using Ethylenediaminetetraacetic Acid

Costello, Laurence R.; Bassham, James A.; Calvin, Melvin

doi:10.1104/pp.69.1.77

Cited by 25 publications

(10 citation statements)

References 12 publications

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“…The technique has the added advantage that in labeling studies metabolic changes during or after collection from the phloem are eliminated or at least minimized. These are likely to occur with either the EDTA technique (7,13,26,28) or when the bodies of aphids feeding on phloem are used to collect phloemborne assimilates (4).…”

Section: Discussionmentioning

confidence: 99%

Spontaneous Phloem Bleeding from Cryopunctured Fruits of a Ureide-Producing Legume

Pate¹,

Peoples²,

Atkins³

1984

Plant Physiol.

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The vasculature of the dorsal suture of cowpea (Vigna uagwicalata IL.] Walp) fruits bled a sugar-rich exudate when punctured with a fie needle previously cooled in liquid N2. Bleeding continued for many days at rates equivalent to 10% of the estimated current sugar intake of the fruit. A phloem origin for the exudate was suggested from its high levels (0.4-0.8 millimoles per milliliter) of sugar (98% of this as sucrose) and its high K' content and high ratio of Mg2e to Ca2l. Fruit cryopuncture sap became labeled with 14C following feeding of I'jqurea to leaves or adjacent walls of the fruit, of '4CO2 to the pod gas space, and of I1'4C asparagine or '4Callantoin to leaflets or cut shoots through the xylem.Rates of translocation of 14C-assimilates from a fed leaf to the puncture site on a subtended fruit were 21 to 38 centimeters per hour. Analysis of '4C distribution in phloem sap suggested that I'4Caflantoin was metabolized to a greater extent in its passage to the fruit than was 1'Cj to puncture the vascular strands of the mid-dorsal suture of a fruit with the tip of a fine (0.5-mm) needle previously cooled in liquid N2, retaining the needle tip in the fruit for a period of 5 s to allow chilling of tissues in the immediate vicinity of the puncture. This treatment induced bleeding usually within 30 min ofpuncture and by placing microcapillaries (1-5 Ml capacity) over the wound, the exudate was readily collected. Collection periods ranged from 30 min to several days depending on the nature of the experiment. Time courses of bleeding (labeled or unlabeled sap) from single sites were followed by regularly changing microcapillaries trapping the exuded sap. Cryopuncturing of fruits was attempted day and night on fruits aged 6 to 18 d after anthesis. Sap collected over several hours of bleeding from 30 or more similar fruits was combined to provide samples of 0.5 to 1.5 ml, enabling a variety ofanalyses to be conducted on a single sap sample.

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Section: Discussionmentioning

confidence: 99%

Spontaneous Phloem Bleeding from Cryopunctured Fruits of a Ureide-Producing Legume

Pate¹,

Peoples²,

Atkins³

1984

Plant Physiol.

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“…Efficient and longterm exudation usually is achieved by adding EDTA to the medium; EDTA is thought to inhibit or at least reduce the formation of wound callose in sieve pores by chelating Ca 2+ (40,41). However, callose depositions in sieve pores are known to promote the long-term sealing of sieve plates (42,43), and at least several minutes pass before the pores are fully sealed (44).…”

Section: Ntseo-knockdown Plants Show Enhanced Bleeding After Woundingmentioning

confidence: 99%

Sieve element occlusion(SEO) genes encode structural phloem proteins involved in wound sealing of the phloem

Ernst

Jekat

Zielonka

et al. 2012

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

100

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The sieve element occlusion (SEO) gene family originally was delimited to genes encoding structural components of forisomes, which are specialized crystalloid phloem proteins found solely in the Fabaceae. More recently, SEO genes discovered in various nonFabaceae plants were proposed to encode the common phloem proteins (P-proteins) that plug sieve plates after wounding. We carried out a comprehensive characterization of two tobacco (Nicotiana tabacum) SEO genes (NtSEO). Reporter genes controlled by the NtSEO promoters were expressed specifically in immature sieve elements, and GFP-SEO fusion proteins formed parietal agglomerates in intact sieve elements as well as sieve plate plugs after wounding. NtSEO proteins with and without fluorescent protein tags formed agglomerates similar in structure to native Pprotein bodies when transiently coexpressed in Nicotiana benthamiana, and the analysis of these protein complexes by electron microscopy revealed ultrastructural features resembling those of native P-proteins. NtSEO-RNA interference lines were essentially devoid of P-protein structures and lost photoassimilates more rapidly after injury than control plants, thus confirming the role of P-proteins in sieve tube sealing. We therefore provide direct evidence that SEO genes in tobacco encode P-protein subunits that affect translocation. We also found that peptides recently identified in fascicular phloem P-protein plugs from squash (Cucurbita maxima) represent cucurbit members of the SEO family. Our results therefore suggest a common evolutionary origin for P-proteins found in the sieve elements of all dicotyledonous plants and demonstrate the exceptional status of extrafascicular P-proteins in cucurbits.photoassimilate transport | wound response | exudation | phloem protein 1

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“…The total amount of Suc, Glc, and Fru exuded from groups of three rosette leaves within a given time interval was assayed using an established procedure (Costello et al, 1982), with modifications that have been described previously (Chia et al, 2000).…”

Section: Phloem Exudation Assaysmentioning

confidence: 99%

The ram1 Mutant of Arabidopsis Exhibits Severely Decreased β-Amylase Activity

2001

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Despite extensive biochemical analyses, the biological function(s) of plant ␤-amylases remains unclear. The fact that ␤-amylases degrade starch in vitro suggests that they may play a role in starch metabolism in vivo. ␤-Amylases have also been suggested to prevent the accumulation of highly polymerized polysaccharides that might otherwise impede flux through phloem sieve pores. The identification and characterization of a mutant of Arabidopsis var. Columbia with greatly reduced levels of ␤-amylase activity is reported here. The reduced ␤-amylase 1 (ram1) mutation lies in the gene encoding the major form of ␤-amylase in Arabidopsis. Although the Arabidopsis genome contains nine known or putative ␤-amylase genes, the fact that the ram1 mutation results in almost complete loss of ␤-amylase activity in rosette leaves and inflorescences (stems) indicates that the gene affected by the ram1 mutation is responsible for most of the ␤-amylase activity present in these tissues. The leaves of ram1 plants accumulate wild-type levels of starch, soluble sugars, anthocyanin, and chlorophyll. Plants carrying the ram1 mutation also exhibit wild-type rates of phloem exudation and of overall growth. These results suggest that little to no ␤-amylase activity is required to maintain normal starch levels, rates of phloem exudation, and overall plant growth.␤-Amylases are found in vegetative tissues as well as in storage and reproductive organs, such as tubers and seeds. ␤-Amylases hydrolyze ␣-1,4-glucosidic linkages from the reducing ends of polysaccharide chains to form maltose (Beck and Ziegler, 1989). The genomes of many plant species contain several genes that encode ␤-amylases. For example, according to the database maintained by The Institute for Genomic Research (TIGR), the Arabidopsis genome includes nine genes that are identified as ␤-amylase or putative ␤-amylase genes (http://www.tigr.org/ tdb/edb2/ath1/htmls/GeneNameSearch.html). Despite the fact that they have been well characterized in vitro, the in vivo biological function(s) of ␤-amylases remains under debate (Ziegler, 1999).Several functions have been proposed for ␤-amylases in vivo. The fact that ␤-amylases hydrolyze starch in vitro (Beck and Ziegler, 1989) suggests a role for ␤-amylases in starch degradation. In addition, immunolocalization studies have shown an apparent association between ␤-amylases and starch granules (Okamoto and Akazawa, 1979;Hagenimana et al., 1992). However, these studies were conducted using polyclonal antibodies that may cross-react with starch phosphorylase. Consequently, the results of these studies should be interpreted with caution (Wang et al., 1995). In addition, starch is localized to plastids, whereas most ␤-amylases lack chloroplast transit peptides (Kreis et al., 1987;Monroe et al., 1991;Yoshida and Nakamura, 1991). Although chloroplast-localized ␤-amylases have been identified (Lao et al., 1999), the majority of ␤-amylase activity is extrachloroplastic (Beck and Ziegler, 1989;Nakamura et al., 1991). For example, 80% of the amylas...

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Enhancement of Phloem Exudation from Fraxinus uhdei Wenz. (Evergreen Ash) using Ethylenediaminetetraacetic Acid

Cited by 25 publications

References 12 publications

Spontaneous Phloem Bleeding from Cryopunctured Fruits of a Ureide-Producing Legume

Spontaneous Phloem Bleeding from Cryopunctured Fruits of a Ureide-Producing Legume

Sieve element occlusion(SEO) genes encode structural phloem proteins involved in wound sealing of the phloem

The ram1 Mutant of Arabidopsis Exhibits Severely Decreased β-Amylase Activity

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