Читать книгу Biotechnology of Fruit and Nut Crops - Группа авторов - Страница 14

Molecular studies of Actinidia species initially focused on cloning several genes of interest, especially those expressed in fruit tissues. Most of the early information was reviewed in the first edition of this chapter (Oliveira and Fraser, 2005). More recently, the characterization of new genes, in many cases cloned from a kiwifruit expressed sequence tag (EST) database and involved in different aspects of fruit development, have been reported. These include six lipoxygenase enzyme (LOX) genes related to aroma production (Zhang et al., 2006), two lycopene beta-cyclase (LCY-β) genes associated with carotenoid accumulation (Ampomah-Dwamena et al., 2009), 14 xyloglucan endotransglucosylase/hydrolase (XTH) genes involved in fruit ripening (Atkinson et al., 2009) and an L-galactose guanyltransferase gene encoding an enzyme involved in ascorbate biosynthesis (Laing et al., 2007). Two glycosyltransferase genes, F3GT1 and F3GGT1, involved in the anthocyanin and flavonoid biosynthetic pathway were identified from red-fleshed kiwifruit (Montefiori et al., 2011), and an L-galactose dehydrogenase (AlGalDH) gene was cloned from Actinidia latifolia (Shang et al., 2009). The recent publication of a transcriptome profiling during fruit development and ripening (Tang et al., 2016) will encourage further studies.

Several aspects of flowering, a critical developmental process for kiwifruit, have gained interest. Walton et al. (2001) identified fragments with homology to the floral meristem identity genes LFY and AP1, and nine MADS-box genes (FUL-like, FUL, AP3-1, AP3-2, PI, AG, SEP1, SEP3 and SEP4) required for floral meristem and floral organ specification have been identified and functionally characterized (Varkonyi-Gasic et al., 2011). Also, SVP-like (short vegetative phase) genes have been identified, with potentially distinct roles in bud dormancy and flowering (Wu et al., 2012b, 2017). The genes encoding SOC1 and FT, integrators of endogenous and environmental signals to promote flowering, have also been identified and characterized (Varkonyi-Gasic et al., 2013; Voogd et al., 2015, 2017). Other aspects of flower development that have been addressed include the characterization of two terpene synthases that could account for the major floral sesquiterpene volatiles observed in both male and female A. deliciosa flowers (Nieuwenhuizen et al., 2009) and an (S)-linalool synthase gene encoding a terpene synthase related to floral aroma in A. arguta (Chen et al., 2010).

The identification of genes involved in sex determination has been an early research goal. The accumulating genetic evidence for sex determination suggests that an active Y system functions in Actinidia with maleness determined by two linked and dominant loci mapped in a 1-Mb subtelomeric region on chromosome 25 (Fraser et al., 2009; Zhang et al., 2015b). The genes contained in this region are unknown, although Kim et al. (2010a) identified, among 15 differentially expressed genes in male and female flowers, two with known functions. These encode a pectin methyl esterase, with functions in pollen development, and an adenosine diphosphate (ADP)-ribosylation factor, with essential roles in vesicle trafficking.