Modulation of Cell Proliferation by Heterotrimeric G Protein in
            <i>Arabidopsis</i>

Ullah, Hemayet; Chen, Jay; Young, Jeff C.; Im, Kyung˗Hoan; Sussman, Michael R.; Jones, Alan M.

doi:10.1126/science.1059040

Cited by 349 publications

(325 citation statements)

References 28 publications

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“…Root length of the gpa1-3 mutant was indistinguishable from wild type, as has also been previously reported for light-grown plants Pandey et al, 2006;Ullah et al, 2003). As reported before Lease et al, 2001;Ullah et al, 2001Ullah et al, , 2003, mature rosettes of the gpa1 and the agb1 mutants have rounded rosette leaves and a smaller rosette diameter relative to wild type, whereas the xlg triple mutant is indistinguishable from wild type at this developmental stage ( Figure S6b). Unlike the agb1 mutants, which have shorter but wider siliques with blunt tips (Lease et al, 2001), the xlg triple mutant siliques exhibit a wild-type morphology (data not shown).…”

Section: Comparison Of Xlgs and Heterotrimeric G Proteinssupporting

confidence: 63%

“…For elongation of primary roots GPA1 is a positive regulator Ullah et al, 2001), whereas the XLGs are negative regulators. gpa1 roots are moderately hypersensitive to growth inhibition by 6% glucose or 1 lM ABA (Huang et al, 2006;Pandey et al, 2006); xlg triple mutant roots are also hypersensitive to 6% glucose, but as an osmotic stress, and are ABA hyposensitive.…”

Section: Xlgs and Heterotrimeric G Proteins In Arabidopsismentioning

confidence: 99%

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Arabidopsis extra‐large G proteins (XLGs) regulate root morphogenesis

Ding

Pandey

Assmann³

2007

The Plant Journal

111

129

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SummaryAs in mammalian systems, heterotrimeric G proteins, composed of a, b and c subunits, are present in plants and are involved in the regulation of development and cell signaling. Besides the sole prototypical G protein a subunit gene, GPA1, the Arabidopsis thaliana genome has three extra-large GTP-binding protein (XLG)-encoding genes: XLG1 (At2g23460), XLG2 (At4g34390) and XLG3 (At1g31930). The C-termini of the XLGs are Ga domains that are homologous to GPA1, whereas their N-termini each contain a cysteine-rich region and a putative nuclear localization signal (NLS). GFP fusions with each XLG confirmed nuclear localization. All three XLG genes are expressed in essentially all plant organs, with strong expression in vascular tissues, primary root meristems and lateral root primordia. Analysis of single, double and triple T-DNA insertional mutants of the XLG genes revealed redundancy in XLG function. Dark-grown xlg1-1 xlg2-1 xlg3-1 triple mutant plants showed markedly increased primary root length compared with wild-type plants. This phenotype was not observed in dark-grown xlg single mutants, and was suppressed upon complementation of the xlg triple mutant with each XLG. Root cell sizes of the xlg triple mutant and root morphology were highly similar to those of wild-type roots, suggesting that XLGs may regulate cell proliferation. Dark-grown roots of the xlg triple mutants also showed altered sensitivity to sugars, ABA hyposensitivity and ethylene hypersensitivity, whereas seed germination in xlg triple mutants was hypersensitive to osmotic stress and ABA. As plantspecific proteins, regulatory mechanisms of XLGs may differ from those of conventional Gas.

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Section: Comparison Of Xlgs and Heterotrimeric G Proteinssupporting

confidence: 63%

Section: Xlgs and Heterotrimeric G Proteins In Arabidopsismentioning

confidence: 99%

Arabidopsis extra‐large G proteins (XLGs) regulate root morphogenesis

Ding

Pandey

Assmann³

2007

The Plant Journal

111

129

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“…The reduction in cell number in G protein mutants is compensated in many cases by cell elongation to achieve nearly normal morphology. Nonetheless, G protein mutants have altered sensitivities to several hormones (Ashikari et al, 1999;Fujisawa et al, 1999;Ueguchi-Tanaka et al, 2000;Ullah et al, 2001Ullah et al, , 2002Ullah et al, , 2003Wang et al, 2001). The reduced perception of some hormones and the complete loss in others in the G protein mutants must impact cellular responsiveness to many signals.…”

Section: Resultsmentioning

confidence: 99%

A Reevaluation of the Role of the Heterotrimeric G Protein in Coupling Light Responses in Arabidopsis

2003

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Previous studies implicated the involvement of a heterotrimeric G protein in red (R) and far-red (FR) light signal transduction, but these studies utilized pharmacological or gain-of-function approaches and, therefore, are indirect tests. Here, we reexamine the role of the single canonical heterotrimeric G protein in R and FR control of hypocotyl growth using a loss-of-function approach. Single-and double-null mutants for the GPA1, AGB1 genes encoding the alpha and beta subunit of the heterotrimeric G protein, respectively, have wild-type sensitivity to R and FR. Ectopic overexpression of wild type and a constitutive active form of the alpha subunit and of the wild-type beta subunit had no effect that can be unequivocally attributed to altered R and FR responsiveness. These results preclude a direct role for the heterotrimeric G complex in R and FR transduction in Arabidopsis leading to growth control in the hypocotyl.The classic example of the molecular coupling of signals by a heterotrimeric G protein to a downstream effector is vision in animals where the alpha subunit of the cognate heterotrimeric complex, transducin, couples the activated heptahelical membrane receptor rhodopsin to its cGMP phosphodiesterase effector in rod photoreceptor cells (Baylor, 1996). Plant cells are also light sensitive, especially in the red (R)/far-red (FR) light spectral region due to its highly light-sensitive family of photoreceptors called phytochrome. Therefore, an obvious question has been whether phytochrome light perception is similarly coupled by a heterotrimeric G protein to an unidentified downstream effector. Two influential papers of the early 1990s suggested that it is (Bowler et al., 1994;Neuhaus et al., 1993). In these elegant studies, some phenotypes of a tomato (Lycopersicon esculentum) phytochrome mutant could be rescued to wild type by pertussis and cholera toxins, agents that stabilize the activated form of the G protein subunit by different means. Furthermore, microinjection of cGMP induced some phytochrome-mediated events in the dark. These observations led these authors to conclude that a heterotrimeric G protein was positioned downstream of phytochrome in the light signal transduction pathway and upstream of a cGMPmediated step, in analogy to light perception in animals. Several other labs used pharmacological approaches in different systems and came to the same conclusion. Electroporation of GDP␤S blocked R-induced protoplast swelling, whereas GTP␥S induced swelling in darkness (Bosson et al., 1990). Cholera toxin was shown to increase the steady-state mRNA levels of the light-regulated gene, CAB (Romero and Lam, 1993).More recently, Okamota and colleagues took a gain-of-function approach to test this hypothesis and concluded with all previous authors that a heterotrimeric G protein is involved in phytochromemediated signal transduction (Okamota et al., 2001). The authors reported that Arabidopsis ectopically overexpressing the alpha subunit of the heterotrimeric G protein, regardless of the G␣ activatio...

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“…In contrast, plant genomes contain a single copy of the Gα coding gene [2]. Nevertheless, recent studies in Arabidopsis have shown that plant G protein signaling is important to many fundamental processes, such as cell proliferation, hormone perception and ionchannel regulation [3,4]. In rice, the G protein α subunit was first cloned and characterized in 1995 and designated RGA1 (rice G protein α subunit 1) [5,6].…”

Section: Introductionmentioning

confidence: 99%

Heterotrimeric G protein α subunit is involved in rice brassinosteroid response

Wang

et al. 2006

Cell Res

111

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Heterotrimeric G proteins are known to function as messengers in numerous signal transduction pathways. The null mutation of RGA (rice heterotrimeric G protein α subunit), which encodes the α subunit of heterotrimeric G protein in rice, causes severe dwarfism and reduced responsiveness to gibberellic acid in rice. However, less is known about heterotrimeric G protein in brassinosteroid (BR) signaling, one of the well-understood phytohormone pathways. In the present study, we used root elongation inhibition assay, lamina inclination assay and coleoptile elongation analysis to demonstrated reduced sensitivity of d1 mutant plants (caused by the null mutation of RGA) to 24-epibrassinolide (24-epiBL), which belongs to brassinosteroids and plays a wide variety of roles in plant growth and development. Moreover, RGA transcript level was decreased in 24-epiBL-treated seedlings in a dose-dependent manner. Our results show that RGA is involved in rice brassinosteroid response, which may be beneficial to elucidate the molecular mechanisms of G protein signaling and provide a novel perspective to understand BR signaling in higher plants.

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Modulation of Cell Proliferation by Heterotrimeric G Protein in Arabidopsis

Cited by 349 publications

References 28 publications

Arabidopsis extra‐large G proteins (XLGs) regulate root morphogenesis

Arabidopsis extra‐large G proteins (XLGs) regulate root morphogenesis

A Reevaluation of the Role of the Heterotrimeric G Protein in Coupling Light Responses in Arabidopsis

Heterotrimeric G protein α subunit is involved in rice brassinosteroid response

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