79thCRC Seminar
Dr. Gloria Muday
Biology Department
Wake Forest University, Winston-Salem, USA
Dr. Gloria Muday of Wake Forest University is the speaker of 79thCRC seminar. Dr. Muday is a leading
scientist in the field of hormonal growth and regulation with an extensive expertise in auxin and ethylene.
Recently her group has taken a transcriptional profiling approach in understanding the molecular basesof auxin-ethylene crosstalk. Dr. Muday will introduce the data and discuss on yet unidentified potential
pathways that regulate root developmental processes through modulating auxin-ethylene interaction.

“Transcriptional events that mediate the synergistic andantagonistic actions of auxin and ethylene on root growthand development”
᫬㛫㸸2013 ᖺ 07 ᭶ 3 ᪥㸦Ỉ㸧16:30㹼18:00
ሙᡤ㸸⥲ྜᩍ⫱◊✲Ჷ㸦⏕࿨⣔㸧1 㝵 㐲㝸ㅮ⩏ᐊEthylene regulates root elongation and lateral root development by modulating auxin signaling, synthesis, and transport.
Auxin and ethylene synergistically inhibit root elongation while ethylene antagonizes the positive effect of auxin on
lateral root formation. These effects of ethylene on root growth and development are mediated through canonicalethylene signaling pathways identified in regulation of hypocotyl elongation. We utilized genetic and molecularapproaches to identify mechanisms by which ethylene reduces lateral root formation and enhances the polar transport ofthe hormone auxin. Plants with mutations in a subset of auxin influx and efflux proteins are insensitive to the inhibitionof lateral root initiation and the enhancement of auxin transport. The abundance of transcripts encoding the transport
proteins, AUX1, PIN3, and PIN7, are increased by ACC and IAA in an ETR1 and EIN2 (ethylene signaling) dependent
and TIR1 (auxin receptor) dependent fashion, respectively. Using fluorescent protein fusions to these proteins, weobserved that ACC treatment increased PIN3 and PIN7 expression resulting in elevated auxin transport, which
prevented localized accumulation of auxin needed to drive lateral root formation. We have extended this work toidentify the genome wide transcriptional changes in response to these two hormones, to better understand the molecularmechanism for crosstalk between these two hormones. We examined the transcript accumulation profiles in root
samples isolated from seedlings treated with auxin (IAA) or an ethylene precursor (ACC) over an extended time course(from 0.5 to 24 hrs), to identify primary response genes, including transcription factors and signaling proteins, and themore slowly accumulated transcripts encoding proteins that control growth and development. We filtered for genes that
had a consistent magnitude and pattern of expression across 3 biological replicates. We identified 1,246 and 449 genesthat changed consistently in response to IAA or ACC, respectively, with an overlap of 139 genes. This analysis
provided insight into the time course of gene expression changes for genes previously identified as primary auxin- or
ethylene-responsive genes, and identified novel genes with informative patterns of induction or repression. Late genes
whose expression is temporally linked to changing growth and developmental patterns after hormone treatment werealso identified, along with genes whose expression suggests a role in either the synergistic or antagonistic actions of IAAand ACC. The combination of highly reliable kinetic transcript data and the timeline of the response to these hormones
allowed development of hypotheses for transcript/protein function that are being tested by mutant analysis.

㸦ၥྜඛ㸸Abidur Rahman㸸abidur@iwate-u.ac.jp㸧
CRC ࡣᐮ෭ࣂ࢖࢜ࣇࣟࣥࢸ࢕࢔◊✲ࢭࣥࢱ࣮ࡢⱥྡ Cryobiofrontier Research Center ࡢ␎⛠࡛ࡍࠋ