ATL9 is unique among ATL family members that have been characterized since it contains a PEST domain. PEST domains are common in proteins that are rapidly degraded in the cell and are suggested to serve as proteolytic signals involved in ubiquitination and internalization of proteins. While few studies in plants have examined the role of PEST domains and the UPS in defense, there are numerous studies in mammals describing PEST domains and their role in defense against cellular pathogens. The presence of a PEST domain in the ATL9 protein may imply that there are multiple ways to control its expression and that ATL9 may play a critical role in plant defense similar to that of the Mcl family of genes in humans which are necessary for cell survival in the immune system. In plants, the tomato Ve gene contains a PEST domain that is necessary for defense against Verticillim species. Reproductive Gomisin-D development of higher plants entails a succession of developmental steps, from floral bud generation to fruit ripening and seed dispersal, all aimed at ensuring progeny survival. Such biological processes are finely controlled by different transcription factors, most of which belong to the MADS-box family. Extensive genetic and molecular studies performed in several model plant species have led to a broadly accepted model of flower development based on the combinatory activity of three gene Danshensu functions which determine floral organ identity, i.e. the ABC model. More recently, new regulatory functions have been added and a revised model based on the formation of MADS protein complexes has been proposed. As in most flowering plants, fruit development of tomato begins with ovary fecundation and goes through three phases. The earliest one takes place around flower anthesis and involves the development of the carpels forming the ovary and the decision to proceed with fruit development or to abort. During the second phase, the fruit grows due primarily to cell division and the embryos start their development. Accordingly, genes regulating cell division and cell cycle are highly expressed in developing fruits. Cell division ceases at the third phase and fruit growth continues by cell expansion until the fruit achieves its final size. Subsequently, increases in the respiration rate and ethylene synthesis occur in fully developed fruits allowing their ripening. Accordingly, tomato ACS and ACO genes and ethylene receptor genes, mainly NR and ETR4 are activated during fruit ripening. Furthermore, the genetic and physiological characterization of tomato ripening mutants, ripeninginhibitor, non-ripening and Colorless non-ripening, together with the molecular isolation of the mutated genes, have demonstrated that other important regulatory factors must be properly coordinated with the ethylene signal to carry out the ripening program. RIN, NOR and CNR genes encode transcription factors belonging to the MADS-box, NACdomain and SBP-box families, respectively. They act upstream of ethylene biosynthesis and are key functions for the genetic control of fruit ripening. Interestingly, RIN and two regulatory proteins recently reported as involved in fruit ripening, the TAGL1 MADS-box factor and the HB-1 homeobox protein, are able to bind to the promoter region of ACS2 and ACO1 genes, respectively, proving that transcriptional factors directly regulate the activity of ethylene biosynthesis genes in tomato. Besides the regulatory pathways, studies concerning fruit ripening in tomato have also focused on the biochemical and physiological changes taking place during the ripening process, such as chlorophyll degradation, sugar and pigment accumulation, production of aroma and flavour components, cell wall metabolism and softening. Examples of the best characterized ripening genes include those encoding the fruit specific polygalacturonase and pectinesterase, two enzymes involved in cell wall degradation associated to fruit softening, as well as, phytoene synthase, responsible for the synthesis of lycopene, the red pigment characterizing ripe tomatoes.