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Bio 3465 - Plant Physiology (Syllabus
- Lab Syllabus ) Bio 3490 - Principles
of Developmental Biology (Syllabus) Bio 7360P -
Regulation of Plant Growth & Development (Syllabus) Auxin signaling in plants: Plant growth and
development is controlled by several plant hormones. Of these, auxin plays a major role as it regulates growth and
development throughout the life cycle of plants. Indole
acetic acid (IAA) is the major form of auxin in
plants. In addition to IAA, there are number of natural and synthetic
chemicals that have auxin activity. Some of
these chemicals are being used as plant growth regulators and herbicides in
agro-industry. One of the well-characterized activities related to auxin is the rapid modulation of gene expression.
This is achieved through the degradation of group of repressor proteins,
called Aux/IAA proteins. These proteins are degraded through a highly
regulated mechanism known as ubiquitin-proteasome
pathway. Auxin promotes the degradation of Aux/IAA proteins by
enhancing the interaction between Aux/IAA proteins and SCFTIR1 protein complex. The exact molecular mechanism
involved in this activity is not understood completely, however recent
evidence indicates that TIR1 functions as an auxin
receptor in plants. In Arabidopsis, TIR1 belongs to a gene
family. TIR1 related genes in Arabidopsis are known as AFBs.
Genetic studies indicate that loss of TIR1 and AFB functions causes severe
growth and developmental defects. The mechanisms by
which auxins control plant growth and development
are not completely understood. This is especially true for the
downstream targets of auxin signaling. In our lab
we use combination of molecular, genetic and biochemical approaches to understand
the auxin signaling mechanisms in plants. We
use the model plant Arabidopsis thaliana as our experimental organism.
Savaldi-Goldstein S, Baiga TJ, Pojer F, Dabi T, Butterfield C,
Parry G, Sanner A, Dharmasiri N, Tao Y, Estelle M, Noel
JP, Chory J.
(2008) New auxin analogs with growth-promoting
effects in intact plants reveal a chemical strategy to improve hormone
delivery. Proc Natl Acad Sci Dharmasiri N., Dharmasiri S., Weijers D., Karunarathne N., Jurgen G. and
Estelle M. (2007) AXL1 and AXR1 have redundant functions in RUB conjugation
and growth and development in Arabidopsis. Plant J. 52:114-123.
PDF Dharmasiri S, Swarup R, Mockaitis K, Dharmasiri N ,
Singh SK, Kowalchyk M, Marchant
A, Sandberg G, Bennett M, Estelle M. (2006) AXR4 is required for asymmetric
localization of the auxin influx facilitator AUX1. Science
312: 1218-1220. PDF Navarro L., Dunoyer P., Jay F., Arnold B., Dharmasiri
N., Estelle M., Voinnet O., Jones J.D.G (2006)
A plant miRNA contributes to antibacterial
resistance by repressing Auxin signaling. Science. 312:
436-439. PDF Dharmasiri N, Dharmasiri S and Estelle M (2005) The F-box protein TIR1
is an auxin receptor. Nature. 435:
441- 445. PDF Dharmasiri N, Dharmasiri S, Weijers D, Lechner E, Yamada M, Hobbie L, Eismann JS, Jurgens G and
Estelle M (2005) Plant development is regulated by a family of auxin receptor F box proteins. Dev. Cell.
9: 109-119. PDF Dharmasiri N. and Estelle,
M. (2004) Auxin signaling and regulated protein
degradation. Trends Plant Sci. 9:302-308. PDF Xiaoqing Yang X., Lee S., Soo J-H, Dharmasiri S., Dharmasiri
N., Lei G., Jensen C., Hangarter R., Hobbie L. and Estelle M. (2004) The IAA1 protein is
encoded by AXR5 and is a substrate of SCFTIR1. Plant J.
40:772-782. PDF Dharmasiri N, Dharmasiri S, Jones AM, Estelle M. (2003) Auxin action in a cell-free system. Curr
Biol. 13(16): 1418-22. PDF
Hellmann H, Hobbie L, Chapman A, Dharmasiri
S, Dharmasiri N, del Pozo C, Reinhardt D, Estelle M. (2003) Arabidopsis AXR6
encodes CUL1 implicating SCF E3 ligases in auxin regulation of embryogenesis. EMBO J.
22(13): 3314-25. PDF Dharmasiri S, Dharmasiri N,
Hellmann H, Estelle M. (2003) The RUB/Nedd8 conjugation pathway is required
for early development in Arabidopsis. EMBO J. 22(8):1762-70.
PDF Liu S, Bugos RC, Dharmasiri
N, Su WW. (2001) Green fluorescent protein as a secretory
reporter and a tool for process optimization in transgenic plant cell
cultures. J Biotechnol. 87(1): 1-16.
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©
2004 Texas State University Biology Department