Poster: Water Relations

Abs # 222: Essentiality of an Aquaporin in Seedling Establishment

Presenter:	Ma, Shisong , sma2@uiuc.edu
Authors	Ma, Shisong  (A)   Quigley, Francoise  (B)   Bohnert, Hans J. (A)
Affiliations:	(A): Physiological and Molecular Plant Biology Graduate Program, University of Illinois (B): Laboratoire de Genetique Moleculaire des Plantes, Université Joseph Fourier

For studying functions of aquaporins (MIPs, water channels) we introduced gene constructs potentially leading to RNA interference (RNAi) effects into Arabidopsis thaliana. The constructs produced double strand RNA (dsRNA) from partial aquaporin coding regions after transfer into wild type Col-O that were monitored by RT-PCR analysis. Eleven individual AQP genes were targeted, we report here the effect of RNAi-based gene silencing on aquaporin gTIP (TIP1;1; At2g36830). Lines with high RNAi expression against the tonoplast-localized gTIP significantly affected the growth of young plants. Among 44 lines (3-week-old primary transformants), 5 died after transfer to soil, 9 developed yellow leaves, and remained at ~15% of wt size (I), 13 grew to ~35% of wt size (II), again with rapidly senescing leaves, and 17 grew similar to wt (III). Gene expression measured by real-time PCR showed class I gTIP mRNA levels at less than 2% of wt, and for intermediate size plants at ~5% compared to wild type. Plant phenotype correlated with the severity of the RNAi effect. Additionally, intermediate size plants were characterized by rapid senescence of silique petioles even under well-watered conditions. The phenotype is confined to young plants and persists in the next generation. The surviving plantlets recovered and developed normally later, suggesting that a different AQP fulfills the role of gTIP in mature plants. The observation of a phenotype in plants that showed less than 10% of the gTIP transcript suggests either the involvement of other AQPs in water homeostasis in young Arabidopsis, considerable redundancy of the water permeation function provided by gTIP, or reflects protein half-life and post-translational regulation of protein amount (supported in part by NSF, DBI-0223905).