Life with and without AtTIP1;1, an Arabidopsis aquaporin preferentially localized in the apposing tonoplasts of adjacent vacuoles.

The Arabidopsis thaliana Tonoplast Intrinsic Protein 1;1 (AtTIP1;1) is a member of the tonoplast aquaporin family. The tissue-specific expression pattern and intracellular localization of AtTIP1;1 were characterized using GUS and GFP fusion genes. Results indicate that AtTIP1;1 is expressed in almost all cell types with the notable exception of meristematic cells.

Novel tonoplast transporters identified using a proteomic approach with vacuoles isolated from cauliflower buds.

Young meristematic plant cells contain a large number of small vacuoles, while the largest part of the vacuome in mature cells is composed by a large central vacuole, occupying 80% to 90% of the cell volume. Thus far, only a limited number of vacuolar membrane proteins have been identified and characterized. The proteomic approach is a powerful tool to identify new vacuolar membrane proteins.

Reticulon-like proteins in Arabidopsis thaliana: structural organization and ER localization.

Reticulons are proteins that have been found predominantly associated with the endoplasmic reticulum in yeast and mammalian cells. While their functions are still poorly understood, recent findings suggest that they participate in the shaping of the tubular endoplamic reticulum (ER). Although reticulon-like proteins have been identified in plants, very little is known about their cellular localization and functions.

Identification, expression, and functional analyses of a thylakoid ATP/ADP carrier from Arabidopsis.

In plants the chloroplast thylakoid membrane is the site of light-dependent photosynthetic reactions coupled to ATP synthesis. The ability of the plant cell to build and alter this membrane system is essential for efficient photosynthesis. A nucleotide translocator homologous to the bovine mitochondrial ADP/ATP carrier (AAC) was previously found in spinach thylakoids.

Autophagy in development and stress responses of plants.

The uptake and degradation of cytoplasmic material by vacuolar autophagy in plants has been studied extensively by electron microscopy and shown to be involved in developmental processes such as vacuole formation, deposition of seed storage proteins and senescence, and in the response of plants to nutrient starvation and to pathogens. The isolation of genes required for autophagy in yeast has allowed the identification of many of the corresponding Arabidopsis genes based on sequence similarity. Knockout mutations in some of these Arabidopsis genes have revealed physiological roles for autophagy in nutrient recycling during nitrogen deficiency and in senescence.

Starvation-induced expression of autophagy-related genes in Arabidopsis.

Background Information: Autophagy is a catabolic process for degradation of cytoplasmic components in the vacuolar apparatus. A genome-wide survey recently showed evolutionary conservation among autophagy genes in yeast, mammals and plants. To elucidate the molecular and subcellular machinery responsible for the sequestration and subsequent digestion of intracellular material in plants, we utilized a combination of morphological and molecular methods (confocal laser-scanning microscopy, transmission electron microscopy and real-time PCR respectively).

New insights into the tonoplast architecture of plant vacuoles and vacuolar dynamics during osmotic stress.

Background: The vegetative plant vacuole occupies >90% of the volume in mature plant cells. Vacuoles play fundamental roles in adjusting cellular homeostasis and allowing cell growth. The composition of the vacuole and the regulation of its volume depend on the coordinated activities of the transporters and channels localized in the membrane (named tonoplast) surrounding the vacuole.

The yeast osmosensitive mutant fps1Delta transformed by the cauliflower BobTIP1;1 aquaporin withstand a hypo-osmotic shock.

Osmoregulation plays an important role in cellular responses to osmotic stress in plants and in yeast. Aquaporins contribute to osmotic adjustment by facilitating transport of water or solutes across membranes. The tonoplastic water channel BobTIP1;1 (original name BobTIP26-1) genes are upregulated during dessication stress in cauliflower meristematic tissue.

Expression of a cauliflower tonoplast aquaporin tagged with GFP in tobacco suspension cells correlates with an increase in cell size.

In plants, vacuoles are essential organelles that undergo dynamic volume changes during cell growth due to rapid and high flow of water through tonoplast water-carrying channels composed of integral proteins (tonoplast aquaporins). The tonoplast BobTIP26-1 from cauliflower has previously been shown to be an efficient active aquaporin in Xenopus leavis oocytes. In this study we used tobacco (Nicotiana tabacum cv.