In plants, sex determination is the processthrough which unisexual flowers are formed.
There are two dominant ways ofunisexual flower development: One is the emergence of only one type of sexorgan without formation of any bisexual tissue at any stage floral development.Whereas in other; there is initiation of a bisexual floral meristem with bothstamens and pistils followed by a developmental arrest or abortion of one sexwith only the stamens or the carpels attaining functional maturity. The stepimpeding the development of floral sex organs is at an immature stage wellprior to reaching sexual maturity (reviewed by Kinney, Columbus, & Friar,2008). Many monoecious species progresses through an early hermaphroditic stageto differentiated (unisexual) stages later in floral development, by abortingor arresting either of the sexual organs (Ainsworth, 2000). Jatropha being a monoeciousplant, sexual differentiation occurs by abortion of stamens, allowing thefemale flowers to develop. No female tissues were found in fully developed maleflowers however remains of male tissues (aborted stamens) were found in a fullydeveloped female flowers. Transcriptome analysis of Jatropha floral budsidentifies Tasselseed 2 (TS2), a sexdetermination gene which is required for stamen development and its reducedexpression promotes the carpel development by aborting male tissues. Recently,transcriptome analysis of male and female floral buds at differentdevelopmental stages of Jatropha identifies CRABS CLAW gene for sexdifferentiation.
They have also identified an ATP-binding protein promotesstamen degeneration in female flower at later stage of development. Chlorophyll A/B-binding protein, ubiquitincarboxyl-terminal hydrolase and inorganic phosphate transporter contribute tothe female organ development whereas cytochrome C oxidase subunit 1 contributesto the development of the stamen. Gibberellin-regulated protein 4-like proteinand AMP-activated protein kinase genes werefound to be associated with stamen differentiation, whereas auxin responsefactor 6-like protein, AGL-20, CLV1, auxin-induced protein 22D, RING-H2 fingerprotein ATL3J, and r2r3-myb transcription factor contribute to embryo sacdevelopment in female flowers. COX, ARP1, GID1 and auxin-induced protein X10Aare expressed in both male and female flowers (Xu et al 2016). Functional study of JcFT, a floreign and a keyregulator of flowering pathway showed highest expression level in femaleflowers (Li et al 2014). Transcriptome analysis of other monoeciousplants have been performed to identify genes associated with sex determination.In Quercus sober POLYGALACTURONASE-1, CYTOCHOMEP450 and ENDO-BETA-1,3-1,4 GLUCANASEgenes were identified for female flowering and CHALCONE SYNTHASE A, DEFECTIVE IN ANTHER DEHISCENCE1 (DAD1) and4-COURAMATE–CoALIGASE-LIKE 1 werefound to be associated with pollen development (Rocheta et al 2014).
ENDO-BETA-1,3-1,4GLUCANASE gene possibly inhibits the development of male structure in femalesand defect in DAD1 showed defects in anther dehiscence, pollen maturation, andflower opening (Ishiguro et al., 2001). In Ricinus communis PDC related genes (cysteine protease) identified forfemale development and its expression level was increased at the peak of antherabortion (Lorrain et al.
, 2003; Wei et al., 2013). In cucumber sex differentiation has been studied extensively and isgenetically controlled by F locus (for females) and M locus (for male). AMINOCYCLOPROPANE-1-CARBOXYLICACID SYNTHASEs (ACS1 & ACS2), ETR2 and ERS genesassociated with ethylene biosynthesisand signaling pathways were found to be involved in sex determination. ACS1 & ACS2 promotes gynoecia development by inhibiting male reproductive organs (Saitoet al 2007; Boualem et al.
, 20089). ETR2 and ERSI, an ethylene receptors accumulated ingynoecia, thus promoting female development (Yamasaki et al 2001). AMADS-box protein ERAF-17 in cucumber induces female flowering. CTR1-like kinaseprotein (CTR1 and CTR2), negative regulators of ethylene