Punita Nagpal

University of North Carolina at Chapel Hill

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Jason W. Reed

University of North Carolina at Chapel Hill

Joanne Chory

Howard Hughes Medical Institute

Christine Ellis

University of North Carolina at Chapel Hill

Sara E. Ploense

University of North Carolina at Chapel Hill

Paul H. Reeves

University of North Carolina at Chapel Hill

Edward E. Farmer

University of Lausanne

Daniel S. Poole

University of Wisconsin–Madison

Gretchen Hagen

University of Missouri

Brendan Trinidad

University of North Carolina at Chapel Hill

Thomas J. Guilfoyle

University of Missouri

Cooperative Institutions

University of North Carolina at Chapel Hill

Salk Institute for Biological Studies

Howard Hughes Medical Institute

University of California, San Diego

University of Minnesota

Fundación Instituto Leloir

University of Lausanne

Plant (United States)

University of Wisconsin–Madison

Scripps Research Institute

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Mutations in the gene for the red/far-red light receptor phytochrome B alter cell elongation and physiological responses throughout Arabidopsis development.

The Plant Cell (1993)

Jason W. Reed Punita Nagpal Daniel S. Poole M. Furuya J. Chory

Phytochromes are a family of plant photoreceptors that mediate physiological and developmental responses to changes in red and far-red light conditions. In Arabidopsis, there are genes for at least five phytochrome proteins. These photoreceptors control such responses as germination, stem elongation, flowering, gene expression, and chloroplast and leaf development. However, it is not known which red light responses are controlled by which phytochrome species, or whether the different phytochromes have overlapping functions. We report here that previously described hy3 mutants have mutations in the gene coding for phytochrome B (PhyB). These are the first mutations shown to lie in a plant photoreceptor gene. A number of tissues are abnormally elongated in the hy3(phyB) mutants, including hypocotyls, stems, petioles, and root hairs. In addition, the mutants flower earlier than the wild type, and they accumulate less chlorophyll. PhyB thus controls Arabidopsis development at numerous stages and in multiple tissues.

Phytochrome

Phytochrome A

Photomorphogenesis

Phototropism

10.1105/tpc.5.2.147

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Citations (930)

Independent Action of ELF3 and phyB to Control Hypocotyl Elongation and Flowering Time

Carolina Digital Repository (University of North Carolina at Chapel Hill) (2000)

Jason W. Reed Punita Nagpal Ruth Bastow Keely S. Solomon Mandy J. Dowson-Day

Elongation

10.17615/xj6k-dt39

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A gain-of-function mutation inIAA18altersArabidopsisembryonic apical patterning

Development (2009)

Sara E. Ploense Miin‐Feng Wu Punita Nagpal Jason W. Reed

Lateral organ emergence in plant embryos and meristems depends on spatially coordinated auxin transport and auxin response. Here, we report the gain-of-function iaa18-1 mutation in Arabidopsis, which stabilizes the Aux/IAA protein IAA18 and causes aberrant cotyledon placement in embryos. IAA18 was expressed in the apical domain of globular stage embryos, and in the shoot apical meristem and adaxial domain of cotyledons of heart stage embryos. Mutant globular embryos had asymmetric PIN1:GFP expression in the apical domain, indicating that IAA18-1 disrupts auxin transport. Genetic interactions among iaa18-1, loss-of-function mutations in ARF (Auxin response factor) genes and ARF-overexpressing constructs suggest that IAA18-1 inhibits activity of MP/ARF5 and other ARF proteins in the apical domain. The iaa18-1 mutation also increased the frequency of rootless seedlings in mutant backgrounds in which auxin regulation of basal pole development was affected. These results indicate that apical patterning requires Aux/IAA protein turnover, and that apical domain auxin response also influences root formation.

Cotyledon

Polar auxin transport

Organogenesis

10.1242/dev.025932

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Citations (87)

Auxin response factors ARF6 and ARF8 promote jasmonic acid production and flower maturation

Carolina Digital Repository (University of North Carolina at Chapel Hill) (2005)

Punita Nagpal Christine Ellis Hans Weber Sara E. Ploense Lana S. Barkawi

Jasmonic acid

10.17615/4f7d-4844

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A Mutation in the Arabidopsis KT2/KUP2 Potassium Transporter Gene Affects Shoot Cell Expansion

The Plant Cell (2002)

Rangasamy P. Elumalai Punita Nagpal Jason W. Reed

Potassium ions (K+) are the most abundant cations in plants and are necessary for cell growth. Arabidopsis shy3-1 mutant plants have a short hypocotyl, small leaves, and a short flowering stem, and these defects result from decreased cell expansion. The semidominant shy3-1 mutation changes an amino acid in KT2/KUP2, a K+ transporter related to the Escherichia coli Kup protein. Second mutations in the KT2/KUP2/SHY3 gene, including presumed null mutations, suppress the shy3-1 phenotypes. Plants with these intragenic suppressor mutations appear similar to wild-type plants, suggesting that KT2/KUP2/SHY3 acts redundantly with other genes. Expression of the shy3-1 mutant version of KT2/KUP2/SHY3 in wild-type plants confers shy3-1–like phenotypes, indicating that shy3-1 probably either causes a gain of function or creates an interfering protein. The shy3-1 mutation does not eliminate the ability of the KT2/KUP2 cDNA to rescue the growth of a potassium transport-deficient E. coli mutant. A P SHY3::GUS fusion is expressed in growing portions of the plant. These results suggest that KT2/KUP2/SHY3 mediates K+-dependent cell expansion in growing tissues.

Wild type

10.1105/tpc.010322

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Citations (215)

AUXIN RESPONSE FACTOR1 and AUXIN RESPONSE FACTOR2regulate senescence and floral organ abscission in Arabidopsisthaliana

Carolina Digital Repository (University of North Carolina at Chapel Hill) (2005)

Christine Ellis Punita Nagpal Jeffery C. Young Gretchen Hagen Thomas J. Guilfoyle

Abscission

Senescence

10.17615/n4mw-rf70

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Citations (31)

From seed germination to flowering, light controls plant development via the pigment phytochrome.

Proceedings of the National Academy of Sciences (1996)

Joanne Chory Mithu Chatterjee Ron Cook Tedd D. Elich Christian Fankhauser

Plant growth and development are regulated by interactions between the environment and endogenous developmental programs. Of the various environmental factors controlling plant development, light plays an especially important role, in photosynthesis, in seasonal and diurnal time sensing, and as a cue for altering developmental pattern. Recently, several laboratories have devised a variety of genetic screens using Arabidopsis thaliana to dissect the signal transduction pathways of the various photoreceptor systems. Genetic analysis demonstrates that light responses are not simply endpoints of linear signal transduction pathways but are the result of the integration of information from a variety of photoreceptors through a complex network of interacting signaling components. These signaling components include the red/far-red light receptors, phytochromes, at least one blue light receptor, and negative regulatory genes (DET, COP, and FUS) that act downstream from the photoreceptors in the nucleus. In addition, a steroid hormone, brassinolide, also plays a role in light-regulated development and gene expression in Arabidopsis. These molecular and genetic data are allowing us to construct models of the mechanisms by which light controls development and gene expression in Arabidopsis. In the future, this knowledge can be used as a framework for understanding how all land plants respond to changes in their environment.

Phytochrome

Photomorphogenesis

Brassinolide

Genetic screen

Far-red

Phytochrome A

10.1073/pnas.93.22.12066

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Citations (215)

A Regulatory Network for Coordinated Flower Maturation

Carolina Digital Repository (University of North Carolina at Chapel Hill) (2012)

Paul H. Reeves Christine Ellis Sara E. Ploense Miin‐Feng Wu Vandana Yadav

10.17615/qc2e-g010

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Suppression of the ndv mutant phenotype of Rhizobium meliloti by cloned exo genes

Molecular Microbiology (1992)

Punita Nagpal S. P. S. Khanuja S W Stanfield

Summary The ndv A and ndvB genes of Rhizobium meliloti are involved in the export and synthesis, respectively, of the small cyclic polysaccharide β(1,2)glucan. We have previously shown that spontaneous symbiotic pseudorevertants of ndv mutants do not produce periplasmic β(1,2)glucan. Here we show that the pseudorevertants also do not produce extracellular β(1,2)glucan, but do show alterations in the amount of the major acidic exopolysaccharide produced. This exopolysaccharide is not detectably different from that produced by the wild type or by the ndv mutants. A cosmid which suppresses the symbiotic defect of both ndvA and ndvB mutants was isolated from a gene bank prepared from DNA of an ndvA pseudo‐revertant. This cosmid contains a number of exo genes, including exoH and exoF. Subcloning and Tn5 mutagenesis were used to show that the widely separated exoH and exoF genes are both involved in suppression of the ndv mutant phenotype and that the 3.5 kb DNA fragment which contains the exoH gene does not carry the mutation responsible for second site suppression.

Cosmid

Subcloning

10.1111/j.1365-2958.1992.tb01492.x

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Citations (19)

A Regulatory Network for Coordinated Flower Maturation

PLoS Genetics (2012)

Paul H. Reeves Christine Ellis Sara E. Ploense Miin‐Feng Wu Vandana Yadav

For self-pollinating plants to reproduce, male and female organ development must be coordinated as flowers mature. The Arabidopsis transcription factors AUXIN RESPONSE FACTOR 6 (ARF6) and ARF8 regulate this complex process by promoting petal expansion, stamen filament elongation, anther dehiscence, and gynoecium maturation, thereby ensuring that pollen released from the anthers is deposited on the stigma of a receptive gynoecium. ARF6 and ARF8 induce jasmonate production, which in turn triggers expression of MYB21 and MYB24, encoding R2R3 MYB transcription factors that promote petal and stamen growth. To understand the dynamics of this flower maturation regulatory network, we have characterized morphological, chemical, and global gene expression phenotypes of arf, myb, and jasmonate pathway mutant flowers. We found that MYB21 and MYB24 promoted not only petal and stamen development but also gynoecium growth. As well as regulating reproductive competence, both the ARF and MYB factors promoted nectary development or function and volatile sesquiterpene production, which may attract insect pollinators and/or repel pathogens. Mutants lacking jasmonate synthesis or response had decreased MYB21 expression and stamen and petal growth at the stage when flowers normally open, but had increased MYB21 expression in petals of older flowers, resulting in renewed and persistent petal expansion at later stages. Both auxin response and jasmonate synthesis promoted positive feedbacks that may ensure rapid petal and stamen growth as flowers open. MYB21 also fed back negatively on expression of jasmonate biosynthesis pathway genes to decrease flower jasmonate level, which correlated with termination of growth after flowers have opened. These dynamic feedbacks may promote timely, coordinated, and transient growth of flower organs.

Petal

Jasmonate

MYB

Sepal

10.1371/journal.pgen.1002506

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Citations (237)