The majority of higher plants use sucrose as their main mobile carbohydrate. Proton-driven sucrose trans- porters play a crucial role in cell-to-cell and long-distance distribution of sucrose throughout the plant. A v...The majority of higher plants use sucrose as their main mobile carbohydrate. Proton-driven sucrose trans- porters play a crucial role in cell-to-cell and long-distance distribution of sucrose throughout the plant. A very negative plant membrane potential and the ability of sucrose transporters to accumulate sucrose concentrations of more than 1 M indicate that plants evolved transporters with unique structural and functional features. The knowledge about the trans- port mechanism and structural/functional domains of these the current knowledge about the biophysical properties of nano-machines is, however, still fragmentary. In this review, plant sucrose transporters is summarized and discussed.展开更多
Central to understanding fruit development is to elucidate the processes mediating a successful transition from pre-pollination ovaries to newly set fruit, a key step in establishing fruit yield potential. In tomato, ...Central to understanding fruit development is to elucidate the processes mediating a successful transition from pre-pollination ovaries to newly set fruit, a key step in establishing fruit yield potential. In tomato, cell wall invertase （CWIN） LIN5 and its inhibitor INH1 are essential for fruit growth. However, the molecular and cellular basis by which they exert their roles in ovary-to-fruit transition remains unknown. To address this issue, we conducted a study focusing on ovaries and fruitlets at 2 days before and 2 days after anthesis, respectively. In situ hybridization analyses revealed that LIN5 and INH1 exhibited a dispersed expression in ovaries compared with their phloem-specific expression in fruitlets. Remarkably, LIN5 and INH1 proteins were immunologically co-localized to cell walls of sieve elements （SEs） in ovaries immediately prior to anthesis and in young fruitlets, but were undetectable in provascular bundles of younger ovaries. A burst in CWlN activity occurred during ovary-to-fruit transition. Interestingly, the ovaries, but not the fruit- lets, exhibited high expression of a defective invertase, SldeCWIN1, an ortholog of which is known to enhance inhibition of INH on CWlN activity in tobacco. Imaging of a fluorescent symplasmic tracer indicated an apoplasmic phloem unloading pathway operated in ovaries, contrary to the previously observed symplasmic unloading pathway in fruit pericarp. These new data indicate that （1） a phloem-specific patterning of the CWIN and INH mRNAs is induced during ovary-to-fruit transition, and （2） LIN5 protein functions specifically in walls of SEs and increases its activity during ovary-to-fruit transition, probably to facilitate phloem unloading and to generate a glucose signal positively regulating cell division, hence fruit set.展开更多
文摘The majority of higher plants use sucrose as their main mobile carbohydrate. Proton-driven sucrose trans- porters play a crucial role in cell-to-cell and long-distance distribution of sucrose throughout the plant. A very negative plant membrane potential and the ability of sucrose transporters to accumulate sucrose concentrations of more than 1 M indicate that plants evolved transporters with unique structural and functional features. The knowledge about the trans- port mechanism and structural/functional domains of these the current knowledge about the biophysical properties of nano-machines is, however, still fragmentary. In this review, plant sucrose transporters is summarized and discussed.
文摘Central to understanding fruit development is to elucidate the processes mediating a successful transition from pre-pollination ovaries to newly set fruit, a key step in establishing fruit yield potential. In tomato, cell wall invertase （CWIN） LIN5 and its inhibitor INH1 are essential for fruit growth. However, the molecular and cellular basis by which they exert their roles in ovary-to-fruit transition remains unknown. To address this issue, we conducted a study focusing on ovaries and fruitlets at 2 days before and 2 days after anthesis, respectively. In situ hybridization analyses revealed that LIN5 and INH1 exhibited a dispersed expression in ovaries compared with their phloem-specific expression in fruitlets. Remarkably, LIN5 and INH1 proteins were immunologically co-localized to cell walls of sieve elements （SEs） in ovaries immediately prior to anthesis and in young fruitlets, but were undetectable in provascular bundles of younger ovaries. A burst in CWlN activity occurred during ovary-to-fruit transition. Interestingly, the ovaries, but not the fruit- lets, exhibited high expression of a defective invertase, SldeCWIN1, an ortholog of which is known to enhance inhibition of INH on CWlN activity in tobacco. Imaging of a fluorescent symplasmic tracer indicated an apoplasmic phloem unloading pathway operated in ovaries, contrary to the previously observed symplasmic unloading pathway in fruit pericarp. These new data indicate that （1） a phloem-specific patterning of the CWIN and INH mRNAs is induced during ovary-to-fruit transition, and （2） LIN5 protein functions specifically in walls of SEs and increases its activity during ovary-to-fruit transition, probably to facilitate phloem unloading and to generate a glucose signal positively regulating cell division, hence fruit set.
