Loss of TIP1;1 aquaporin in Arabidopsis leads to cell and plant death

Abstract

SummaryArabidopsis TIP1;1 (cTIP) is a member of the tonoplast family of aquaporins (AQP). Using RNA interference (RNA i ) we reduced TIP1;1 to different extent in various lines. When most severely affected, miniature plants died, a phenotype partially complemented by the TIP1;1 homolog McMIP-F. Less severely affected lines produced small plants, early senescence, and showed lesion formation. The relative water content in TIP1;1 RNAi plants was not significantly affected. Global expression profiling suggested a disturbance in carbon metabolism in RNAi lines with upregulated transcripts for functions in carbon acquisition and respiration, vesicle transport, signaling and transcription, and radical oxygen stress. Metabolite profiles showed low glucose, fructose, inositol, and threonic, succinic, fumaric, and malic acids, but sucrose levels were similar to WT. Increased amounts were found for raffinose and several unknown compounds. TIP1;1 RNAi plants also contained high starch and apoplastic carbohydrate increased. A GFP-TIP1;1 fusion protein indicated tonoplast location in spongy mesophyll cells, and high signal intensity in palisade mesophyll associated with vesicles near plastids. Signals in vascular tissues were strongest not only in vesicle-like structures but also outlined large vacuoles. Compromised routing of carbohydrate and lack of sucrose provision for cell-autonomous functions seems to characterize this RNAi phenotype. We suggest a function for TIP1;1 in vesicle-based metabolite routing through or between pre-vacuolar compartments and the central vacuole. Phenotype and expression characteristics support a view of TIP1;1 functioning as a marker for vesicles that are targeted to the central vacuole.

Specific Aquaporins Facilitate the Diffusion of Hydrogen Peroxide across Membranes

“…At the metabolic level, mutants accumulated starch and showed changed sugar content. Based on their results, Ma et al (54) suggested that TIP1;1 may have a role in vesicle trafficking to the central vacuole and vesicle-based metabolite routing in the cell. Thus, they suggested a unique function of TIP1;1.…”

“…In plants, down-regulation of TIP1;1 by RNA interference technology in Arabidopsis resulted in a strong and complex phenotype of early senescence and death (54). F 1 mutants were classified according to the level of expression of the RNA interference construct, which correlated well with the severity of the phenotype.…”

Genetic Control of Carbon Partitioning in Grasses: Roles of Sucrose Transporters and Tie-dyed Loci in Phloem Loading

“…For additional discussions of genes that function in phloem loading and carbon partitioning (e.g. H + -ATPase, K + channel, Suc synthase, aquaporins), we refer interested readers to the following articles (Nolte and Koch, 1993;DeWitt and Sussman, 1995;Hannah et al, 2001;Deeken et al, 2002;Dinges et al, 2003;Ma et al, 2004;Hardin et al, 2006;Lu and Sharkey, 2006;Smith and Stitt, 2007).…”

Isolation of a fruit ripening-related tonoplast aquaporin (GjTIP) gene from Gardenia jasminoides

“…The selectivity filter of AqpZ is the narrowest point in it's water channel, it is formed by the side chains of Phe43, His174, Arg189 and the carbonyl of Thr183,the water in channel forms hydrogen-bond to the carbonyls of T183 (Savage et al 2003). AQGPs usually have Trp-GlaPhe-Arg, some AQGPs have His (Phe)-Ile(His)-Ala(Thr)-Val (Ma et al 2004), their selectivity filters usually are more hydrophobic than in AQPs. GlpF has a much lower conductivity for water than to water channels, the selectivity filter is formed by Trp48, Gla191, Phe200 and Arg206, the phenyl ring of Phe200 and the indole of Trp48 form the hydrophobic corner, they have Van der Waals interaction with the alkyl chain of glycerol, and successive hydroxyl groups form hydrogen bonds with Arg206 and Phe200, and groups of several other amino acids (Fu et al 2000).…”

“…Chilling treatment caused a decrease in the transcript level of OsTIP1;1 in roots, the decreased mRNA levels of OsTIP1;1 were recovered 9 h after warming. Using RNA interference(RNAi), Ma (Ma et al 2004) reduced AtTIP1;1 to different extent in various Arabidopsis lines, when most severely affected, miniature plants died, less severely affected lines produced small plants, early senescence, and showed lesion formation. Analysis of global expression profiling and metabolite profiles suggest a function for TIP1;1 in vesicle-based metabolite routing through or between pre-vacuolar compartments and the central vacuole.…”