Cytokinins in Plant Pathogenic Bacteria and Developing Cereal Grains

Morris, R. O.; Blevins, DG; Dietrich, JT; Durley, Richard C.; Gelvin, SB; Gray, J A; Hommes, Norman G.; Kamínek, M.; Mathews, LJ; Meilan, Richard; Reinbott, T.M.; Sayavedra-Soto, Luis A.

doi:10.1071/pp9930621

Cited by 85 publications

(65 citation statements)

References 52 publications

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“…Our results confirmed early reports (Saha et al, 1986;Morris et al, 1993) that cytokinin contents in rice grains showed a transient increase at early grain filling stage. Our own earlier work (Yang et al, 2000c) with the same rice cultivars observed that maximum cell division rate in endosperm occurred 10 to14 DPA at NN and 12 to 18 DPA at HN.…”

Section: Discussionsupporting

confidence: 82%

“…), high levels of cytokinins are generally found in the endosperm of developing seeds, which may be required for the cell division during the early phase of seed setting (Yang et al, 2000a). Morris et al (1993) reported that zeatin (Z) and zeatin riboside (ZR) in developing rice (Oryza sativa) and wheat (Triticum aestivum) grains showed large transient increases following pollination, which coincided with the period of seed setting and maximum endosperm cell division.…”

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confidence: 99%

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Hormonal Changes in the Grains of Rice Subjected to Water Stress during Grain Filling

et al. 2001

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Lodging-resistant rice (Oryza sativa) cultivars usually show slow grain filling when nitrogen is applied in large amounts. This study investigated the possibility that a hormonal change may mediate the effect of water deficit that enhances whole plant senescence and speeds up grain filling. Two rice cultivars showing high lodging resistance and slow grain filling were field grown and applied with either normal or high amount nitrogen (HN) at heading. Well-watered and water-stressed (WS) treatments were imposed 9 days post anthesis to maturity. Results showed that WS increased partitioning of fixed 14 CO 2 into grains, accelerated the grain filling rate but shortened the grain filling period, whereas the HN did the opposite way. Cytokinin (zeatin ϩ zeatin riboside) and indole-3-acetic acid contents in the grains transiently increased at early filling stage and WS treatments hastened their declines at the late grain filling stage. Gibberellins (GAs; GA 1 ϩ GA 4 ) in the grains were also high at early grain filling but HN enhanced, whereas WS substantially reduced, its accumulation. Opposite to GAs, abscisic acid (ABA) in the grains was low at early grain filling but WS remarkably enhanced its accumulation. The peak values of ABA were significantly correlated with the maximum grain filling rates (r ϭ 0.92**, P Ͻ 0.01) and the partitioning of fixed 14 C into grains (r ϭ 0.95**, P Ͻ 0.01). Exogenously applied ABA on pot-grown HN rice showed similar results as those by WS. Results suggest that an altered hormonal balance in rice grains by water stress during grain filling, especially a decrease in GAs and an increase in ABA, enhances the remobilization of prestored carbon to the grains and accelerates the grain filling rate.

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Section: Discussionsupporting

confidence: 82%

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confidence: 99%

Hormonal Changes in the Grains of Rice Subjected to Water Stress during Grain Filling

et al. 2001

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“…It has been proposed that CK controls seed size by influencing cell number in very young, developing seeds. Increased cell number would enhance storage capacity (Morris et al, 1993;Brenner and Cheikh, 1995). Studies of corn, wheat, and rice (Morris et al, 1993) show that CK content is highest during developmental stages that encompass periods of the most rapid nuclear and cell division of the endosperm.…”

Section: Cis-isomers Of Cytokinin Predominate In Chickpea Seedsmentioning

confidence: 99%

“…Increased cell number would enhance storage capacity (Morris et al, 1993;Brenner and Cheikh, 1995). Studies of corn, wheat, and rice (Morris et al, 1993) show that CK content is highest during developmental stages that encompass periods of the most rapid nuclear and cell division of the endosperm. CK levels are greatest at the early endospermic fluid stages of seed growth in lupin (Davey and van Staden, 1978).…”

Section: Cis-isomers Of Cytokinin Predominate In Chickpea Seedsmentioning

confidence: 99%

cis -Isomers of Cytokinins Predominate in Chickpea Seeds throughout Their Development1

Emery

Leport²,

Barton³

et al. 1998

Plant Physiology

108

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Trans-isomers of cytokinins (CK) are thought to predominate and have greater biological activity than corresponding cis-isomers in higher plants. However, this study demonstrates a system within which the predominant CK are cis-isomers. CK were measured at four developmental stages in developing chickpea (Cicer arietinum L. cultivar Kaniva) seeds by gas chromatography-mass spectrometry. Concentrations were highest at an early endospermic fluid stage and fell considerably when the cotyledons expanded. Seed tissues were the source for isolation of the first naturally occurring CK, trans-Z (Miller, 1961;Letham, 1963). Seeds have turned out to be a rich source of CK, and in the past 30 years investigators have described a range of different CK from seed tissues (van Staden et al., 1982). This may reflect their relatively high levels in seeds (van Staden et al., 1982), a status that is believed to indicate a role for CK in establishing developing seeds as strong assimilate sinks (Brenner and Cheikh, 1995). Despite a vast literature concerning the occurrence, form, and significance of CK in plant development, the nature and site(s) of their synthesis is yet to be established. In fact, Holland (1997) recently proposed that CK are not formed by plants at all but rather by bacterial symbionts that colonize plant tissues. Although there is good evidence for the transfer of CK synthesized by Rhizobium in legume nodules (Upadhyaya et al., 1991), a role for bacteria in providing CK to roots or shoot organs needs to be investigated more thoroughly. Because unequivocal evidence for a plant isopentenyl transferase is lacking, a persistent hypothesis, which has recently been reviewed (Prinsen et al., 1997), is that the free CK in plants are not synthesized de novo but are released during tRNA turnover.Z, [9R-MP]Z, and [9R]Z have an unsaturated isopentenyl side chain that can exist in the cis or trans conformation. The cis-isomer occurs when the hydroxyl group of the isopentenyl side chain is oriented toward the N-1 position of the purine ring, whereas in the trans-isomer the hydroxyl group is oriented away from the purine ring (Korszun et al., 1989; Fig. 1). The trans-isomers of [9R]Z and Z are by far the more commonly reported forms and are considered the predominant isomers in higher plants (McGaw and Burch, 1995;Prinsen et al., 1997). Systems in which the existence of cis-CK can be demonstrated unequivocally would be significant for two reasons. First, because cis-CK show much lower activity than trans-CK in bioassays (Kaminek, 1982) and their interconversion may constitute a mechanism for reducing CK bioactivity in vivo. Second, cis-CK provide evidence for the hypothesis that the free CK pool in higher plants may be at least partially derived from the breakdown of tRNA. The major criticism of this hypothesis has been the structural distinctness between tRNA-bound CK and free-pool CK (Letham and Palni, 1983;McGaw and Burch, 1995;Prinsen et al., 1997

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“…Both RIA and ELISA use radioactively labeled antigen (Ag*) and enzyme-coupled antigen (Ag*) to bind with an antibody to form the specific antigen-antibody (Ag*-Ab) complex, following which the hormones are quantified by measurement of radioactivity and enzyme activity. Immunoassay is a highly specific detection method because of the specific Ab-Ag binding property, and is a sensitive and relatively inexpensive alternative for estimation of plant hormone levels [53][54][55]. The specificity of the Ab-Ag interaction is the key factor affecting quantification results.…”

Section: Immunoassaymentioning

confidence: 99%

Progress in quantitative analysis of plant hormones

Sun

Wang

et al. 2011

Chin. Sci. Bull.

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Plant hormones are small molecular natural products that regulate all plant developmental processes at low concentrations. Quantitative analysis of plant hormones is increasingly important for in-depth study of their biosynthesis, transport, metabolism and molecular regulatory mechanisms. Although plant hormone analysis remains a bottleneck in plant scientific research owing to the trace concentrations and complex components in plant crude extracts, much progress has been achieved in the development of extraction, purification and detection techniques in recent years. Solid phase extraction and chromatography/mass spectrometry have been applied widely for purification and quantitative analysis of plant hormones owing to their high selectivity and sensitivity. Purification methods such as liquid partition and immunoaffinity chromatography, and detection methods including immunoassay and electrochemical analysis, are employed. The advantages and disadvantages of these methods are discussed. In situ, real-time and multi-plant hormone profiling will comprise mainstream techniques for quantitative analyses in future studies on the regulatory mechanisms and crosstalk of plant hormones. defense responses are all triggered by plant hormones. A plant hormone, acting as a plant-development controller or a plant-environment mediator, can influence crop yield directly or indirectly, therefore research into plant hormone physiology has become an important target for agriculture development. However, it is noteworthy that endogenous level of each plant hormone is very low [1], and quantitative analysis of these compounds is still extremely difficult for both biologists and analytical chemists. It is a challenge for researchers to enrich these low-level natural compounds from plant extracts in which large amounts of interfering substances are present. In addition, the limited quantities of plant tissue available for hormone quantification is another challenge. Consequently, the analytic methods must be extremely selective and sensitive. The quantitative analysis of plant hormones typically includes the following key points: (i) the plant materials must

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Cytokinins in Plant Pathogenic Bacteria and Developing Cereal Grains

Cited by 85 publications

References 52 publications

Hormonal Changes in the Grains of Rice Subjected to Water Stress during Grain Filling

Hormonal Changes in the Grains of Rice Subjected to Water Stress during Grain Filling

cis -Isomers of Cytokinins Predominate in Chickpea Seeds throughout Their Development1

Progress in quantitative analysis of plant hormones

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