Developmental Abnormalities and Reduced Fruit Softening in Tomato Plants Expressing an Antisense Rab11 GTPase Gene

Abstract

A cDNA clone from tomato fruit encodes a protein with strong homology with the rab11/YPT3 class of small GTPases that is thought to be involved in the control of protein trafficking within cells. The gene, LeRab11a , showed a pattern consistent with a single copy in DNA gel blots. The corresponding mRNA was developmentally regulated during fruit ripening, and its expression was inhibited in several ripening mutants. Its reduced expression in the Never-ripe mutant indicates that it may be induced by ethylene in fruit. The ripening-induced expression in tissues that are undergoing cell wall loosening immediately suggests a possible role in trafficking of cell wall-modifying enzymes. The message also was produced in leaves and flowers but not in roots. Antisense transformation was used to generate a "mutant phenotype." Antisense fruit changed color as expected but failed to soften normally. This was accompanied by reduced levels of two cell wall hydrolases, pectinesterase and polygalacturonase. There were other phenotypic effects in the plants, including determinate growth, reduced apical dominance, branched inflorescences, abnormal floral structure, and ectopic shoots on the leaves. In some plants, ethylene production was reduced. These data suggest an alternative or additional role in exocytosis or endocytosis of homeotic proteins, hormone carriers, or receptors.

Changes in the microsomal proteome of tomato fruit during ripening

“…The complex metabolic changes that occur during both maturation and ripening, for example in the cell wall, requires also a tight control of the trafficking routes and it is not surprising that the levels of these proteins are maintained constant throughout the ripening process. Perturbation of the trafficking process has a great effect on the fruit phenotype: silencing of the Rab11 GTPase gene leads to reduced levels of pectinesterase and polygalacturonase in the fruit and delayed softening 68 , as well as an increased proportion of cellulose concomitant to a reduction in pectin 44 . SlRab11a may therefore be important for pectin trafficking during fruit development.…”

Biological properties of extracellular vesicles and their physiological functions

“…The protein profile of these EVs was distinct from that of whole sunflower extract and also contained a protein showing 68% identity with human Rab11a GTPase, a mammalian exosome protein identified in several proteomic studies (92) which promotes the docking and the fusion of MVBs with the plasma membrane (556, 684). Rab11 GTPases were also involved in secretion and recycling of cell wall components in tomato (685) and polarized pollen tube growth in tobacco (686). Here, coordinated Rab11 GTPase activity was required for essential membrane trafficking, protein secretion and cell wall modification during fruit ripening.…”

Protein Prenylation in Plant Stress Responses

“…Transgenic tomato plants expressing antisense mRNA for LeRAB11a under the constitutive promoter produced fruits that changed color properly upon the ripening but remained firm for a long time (indicating the possibility for extended storage). The same authors also observed reduced activity of pectinesterase and polygalacturonase in the apoplast of these transgenic tomatoes [75]. Roles of RAB GTPases and other prenylated proteins in plant pathogen resistance have already been mentioned, and research focused on their function should not only bring new interesting discoveries in the near future, but also new biotechnology applications.…”