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

225 WVD2-Like Proteins Regulate Plant Growth Behavior and Overall Morphology
Yan Wang, Jessica Will, Robyn Perrin, Christen Yuen, Patrick Masson
University of Wisconsin-Madison
Arabidopsis plants overexpressing WVD2 (WAVE-DAMPENED2) exhibit dampened root waving and leftward
root skewing when grown on tilted agar surfaces, compared with the wild-type seedlings. They also have shorter and
stockier organs, and their petioles are twisted left-handedly. There are seven WVD2-like (WDL) genes in the Arabidopsis
genome, which share high similarity to WVD2 in a conserved region called the KLEEK domain (Yuen et al., 2003,
Plant Physiology 131: 493-506). Using RT-PCR, we show that these WDL genes are expressed in all tissues examined,
including cotyledons, hypocotyls, seedling roots, stems, flowers, and rosette and cauline leaves. Analysis of transgenic
plants carrying the WDL-GUS transcriptional reporter construct reveals that both WDL1 and WDL4 are highly expressed
in young leaves of seedlings, but show complementary expression patterns in roots. Overexpressing lines for most of the
WDL genes show phenotypes similar to WVD2-overexpressing lines. T-DNA insertional knockout mutants in WDL4 and
WDL5 exhibit stronger rightward skewing on tilted agar plates containing propyzamide or oryzalin (two microtubuledestabilizing
compounds) relative to the wild-type Columbia (Col) seedlings. T-DNA insertional mutants in WDL6 or
WDL7 show altered root growth sensitivity to these compounds but maintain wild-type root skewing. These results
suggest that the WDL genes do not show complete redundancy in regulating root growth and development, and at least
some of the WDL genes may encode proteins that regulate microtubule organization and/or dynamics. We are examining
the global expression patterns and cellular localization of the WDL proteins using GFP and GUS as reporters.
Supported by grants from NASA, NSF and HATCH. RMP was supported by NIH postdoctoral fellowship.
226 The Angiosperm Stem Cell Niche: Recruitment of the WUS/CLV Feedback Loop for Leaf
Development in Grasses
Judith Nardmann, Wolfgang Werr
Institute of Developmental Biology, University of Cologne
In Arabidopsis, stem cell homeostasis in the shoot apical meristem (SAM) is controlled by a feedback loop between
WUS and CLV functions. WUS orthologues were identified in maize and rice by detailed phylogenetic analysis of the
WOX gene family. The allotetraploid maize genome contains two WUS paralogues (ZmWUS1 and ZmWUS2), whereas
a single WUS orthologue is present in the rice genome (OsWUS).
None of the isolated grass WUS orthologues displays an organizing centre-type expression pattern in the vegetative
SAM such as in Arabidopsis. In contrast, the maize and rice WUS expression patterns relate to the specification of new
leaf phytomers. The WUS patterns are consistent with the transcriptional activity of TD1 and FON1 encoding CLV1
orthologues of maize and rice, respectively. The co-recruitment of WUS and CLV1 genes for leaf development implies
co-selection in two grass species without affecting stem cell homeostasis. However, the maize and rice WUS and CLV1
orthologues are co-expressed in all kinds of reproductive meristems where fasciation and supernumerary floral organs
occur in td1 or fon1 loss-of-function mutants. In conclusion, the grass patterns raise doubts about the uniqueness of
WUS/CLV antagonism in the maintenance of the shoot stem cell niche and its general applicability for plant species.