75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

229 Wound-Inducible Upregulation of Trichome Density is Dependent on Jasmonic Acid
Signaling
Yuki Yoshida 1 , Junji Takabayashi 2
1
Graduate School of Science, Kyoto University, 2 Center for Ecological Research, Kyoto University
Spacing of trichomes is important for their functions, one of which is a structural barrier against herbivores. Molecular
genetic studies have revealed that a family of small MYB proteins, including TRIPTYCHON (TRY) and CAPRICE
(CPC), plays a critical role in lateral-inhibition-based patterning of trichomes. Despite the importance of TRY/CPC, it has
been suggested that there are still other unknown pathways to regulate trichome density. We aimed to gain insight into
such novel aspects of trichome patterning. We focused on the wound-inducible upregulation of trichome density, which
was recently reported by Traw and Bergelson (2003). Plastic change in trichome density is observed also in various plant
species other than Arabidopsis, and is generally considered to be an induced defense against herbivory.
Here we show that allene oxide synthase (aos) mutant, defective in jasmonic acid biosynthesis, failed to upregulate
their trichome density when wounded. In normal growth condition, aos mutant produced trichomes comparable to wild
type. CORONATINE INSENSITIVE1 (COI1) encodes an F-box protein essential for jasmonic acid signaling. Like aos
mutant, coi1-1 mutant also failed to increase their trichomes when wounded. These results indicated that both biosynthesis
and SCF COI1 -complex-mediated signaling of jasmonic acid are essential for the regulation of trichome density in response
to wounding, though not required for the normal differentiation of trichome cells. In contrast, other mutants with altered
response to jasmonic acid, namely jasmonate insensitive1-7 (jin1-7) and jasmonate resistant1-1 (jar1-1), did not show
any defects in the wound-responsive upregulation of trichome density, indicating that JIN1 and JAR1 are not required
for the jasmonic acid signaling involved in the regulation of trichome density.
Interestingly, try-29760 and cpc-2 mutants, defective in the lateral inhibition of trichomes, were able to upregulate
their trichome density when treated with jasmonic acid. This raised the possibility that the effect of jasmonic acid on
trichome patterning acts independently from TRY/CPC. Currently, we are further investigating the relationship of jasmonic
acid signaling with TRY/CPC dependent pathway of epidermal pattern formation.
Traw and Bergelson, Plant Physiology 133: 1367-1375 (2003)
230 Studies of Auxin Inducible Genes in Association with Early Transdifferentiation Process into
Tracheary Elements Using cDNA Microarray
Saiko Yoshida 1 , Taku Demura 2 , Hiroo Fukuda 1
1
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2 Plant Science
Center, RIKEN
Apical-basal polar auxin transport is believed to function in the formation of a continuous vascular strand. Polar
auxin transport inhibitors cause ectopic vascular formation at leaf margins and parallel vascular strands at the central
regions. We previously founded that an auxin transport inhibitor, NPA prevented tracheary element (TE) differentiation
from isolated Zinnia mesophyll cells and auxin overcame its prevention. Furthermore, detailed analysis showed that
intracellular free NAA was decreased by the treatment of NPA (Yoshida et al., Plant and Cell Physiology, 46, 2019-28,
2005). It suggested that NPA prevented TE differentiation by decrease of active form of NAA, and the addition of excess
amount of NAA may compensate this depletion. In this study, we performed microarray analysis of genes expressed in
NPA-treated cells and NPA plus NAA-treated cells, to get an insight into auxin regulations of transdifferentiation. The
systematic gene expression analysis revealed that NAA suppressed the expression of wound response genes and promotes
the expression of early xylogenesis/procambium formation-related genes. NAA promoted the expression of Arabidopsis
gene homologues related to auxin signaling, auxin influx, hormone biosynthesis, hormone metabolism, transcription
and transport at early stage of transdifferentiation. Based on these results, auxin action at the transdifferentiation into
tracheary elements is discussed.