ACC Synthase Genes are Polymorphic in Watermelon (Citrullus spp.) and Differentially Expressed in Flowers and in Response to Auxin and Gibberellin

Abstract

The flowering pattern of watermelon species (Citrullus spp.) is either monoecious or andromonoecious. Ethylene is known to play a critical role in floral sex determination of cucurbit species. In contrast to its feminizing effect in cucumber and melon, in watermelon ethylene promotes male flower development. In cucumber, the rate-limiting enzyme of ethylene biosynthesis, 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS), regulates unisexual flower development. To investigate the role of ethylene in flower development, we isolated four genomic sequences of ACS from watermelon (CitACS1-4). Both CitACS1 and CitACS3 are expressed in floral tissue. CitACS1 is also expressed in vegetative tissue and it may be involved in cell growth processes. Expression of CitACS1 is up-regulated by exogenous treatment with auxin, gibberellin or ACC, the immediate precursor of ethylene. No discernible differential floral sex-dependent expression pattern was observed for this gene. The CitACS3 gene is expressed in open flowers and in young staminate floral buds (male or hermaphrodite), but not in female flowers. CitACS3 is also up-regulated by ACC, and is likely to be involved in ethylene-regulated anther development. The expression of CitACS2 was not detected in vegetative or reproductive organs but was up-regulated by auxin. CitACS4 transcript was not detected under our experimental conditions. Restriction fragment length polymorphism (RFLP) and sequence tagged site (STS) marker analyses of the CitACS genes showed polymorphism among and within the different Citrullus groups, including watermelon cultivars, Citrullus lanatus var. lanatus, the central subspecies Citrullus lanatus var. citroides, and the desert species Citrullus colocynthis (L).

Isolation of 1-aminocyclopropane-1-carboxylate synthase gene from Oncidium Gower Ramsey

“…Many studies reported that the ACS genes display distinct spatial and temporal expression patterns (ten Have and Woltering 1997;Trebitsh et al, 1997;Bui and O'Neill, 1998;Jones and Woodson, 1999;Yamasaki et al, 2001;Yamagami et al, 2003;Tsuchisaka and Theologis, 2004;Peng et al, 2005;Salman-Minkov et al, 2008). The expression of the OnACS1 gene in all tissues tested suggests that it is constitutively expressed but at different levels: high levels in gynandria, moderate levels in sepals, and low levels in other organs.…”

Inception of maleness: auxin contribution to flower masculinization in the dioecious cactus Opuntia stenopetala

“…However, the feminizing effect of ethylene is not universal to all the unisexual cucurbits, because in watermelon (Citrullus spp.) ethylene has a masculinizing effect (Salman-Minkov et al 2008).…”

Molecular Characterization of Pear 1-Aminocyclopropane-1-Carboxylate Synthase Gene Preferentially Expressed in Leaves

“…CitACS3 is also up-regulated by ACC, and is likely to be involved in ethylene-regulated anther development. The expression of CitACS2 was not detected in vegetative or reproductive organs (Salman-Minkov et al, 2008). Silencing of ACACS2 causes delayed flowering in pineapple (Trusov et al, 2006).…”

“…Lots of important ACC synthase genes have been isolated and characterized from the plant kingdom. For examples, ACS genes were identified in pear (Pyrus communis) (El-Sharkawy et al, 2004), Japanese pear (Pyrus pyrifolia) (Itai et al, 1999), apple (Rosenfield et al, 1996;Wang et al, 2009), peach (Mathooko et al, 2001;Tatsuki et al, 2006), pineapple (Cazzonelli et al, 1998;Botella et al, 2000;Trusov et al, 2006), plum (El-Sharkawy et al, 2008), cucumber (Mathooko et al, 1999), watermelon (Salman-Minkov et al, 2008), Arabidopsis (Rodrigues-Pousada et al, 1993;Mayer et al, 1999) , tomato (Nakatsuka et al, 1997), etc.…”