Flowerdevelopment and sex determination is highly regulated by crosslink ofendogenous hormones. Auxin plays a pivotal role in regulation of plant growth such as embryogenesis, organogenesis,tropic growth, root architecture, flower and fruit development, tissue andorgan patterning, and vascular development.Primary/early auxin response genesof gene families, auxin/indole-3-acetic acid (Aux/IAA), GretchenHagen3 (GH3), small auxin up RNA (SAUR), and auxin responsefactor (ARF) have been wellknown. In Jatropha,AUX/IAA, SAUR were associated with sex differentiation.
Transcriptome analysis of Jatrophaidentifies genes associated with auxin biosynthesis and signaling such as AUX1, TIR1, AA14 and ARFs. ARFs either activates or represses the expression of auxinresponse genes. In Jatropha,ARF1 acts as atranscriptional repressor and ARF5as a transcriptional activator. Trp-dependent auxin biosynthesis is the main source of auxin productionfor formation reproductive organ and patterning of embryos (wang et al 2015).In this pathway, TAA1/TAR1/TAR2 enzymes produces indole-3-pyruvic acid,which is then converted into IAA by YUCCA (YUC) flavin-dependent monooxygenases(Novak et al., 2012; Korasick et al., 2013; Ljung, 2013; Zhao, 2014).These YUCs produces auxin duringstamen primordia formation by YUC1 and YUC4 and late stamen development by YUC2and YUC6 (Cheng et al.
, 2006; Cecchetti et al., 2008). Inmature gynoecia, YUC4 and YUC8 were expressed in the style and YUC2 in carpelvalve tissues (Cheng et al., 2006; Martínez-Fernández et al., 2014). SPARSE INFLORESCENCE1 (YUC-like) mutants resulted in small ears and fewkernels in maize (Gallavotti et al., 2008a). ).
TAA1 was associated withearly gynoecial development andwas localized within the medial domain of the gynoecia (Stepanova et al., 2008). Increased expression of ARF10,16, 17 and 18 caused floral organ loss and abnormalfemale fertility in Arabidopsis and less seed set rice (Liuet al., 2010, (Huang et al.
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, 2016a). PIN-FORMED (PIN1), an auxin efflux carrier protein hasbeen studied in Arabidopsis for its role in ovule formation. PIN1directs the auxin flow from base of the gynoecium to the top of the gynoecialtube (Larsson et al., 2014; Moubayidin and Østergaard, 2014). BARREN INFLORESCENCE1 (BIF1) and BARRENINFLORESCENCE2 (BIF2)genes identified in maize regulates polar auxin transport via up-regulating PIN1a (Gallavotti et al., 2008b).
bif1 and bif2 mutants havereduced number of spikelets/florets and floral organs, and consequently fewerkernels in maize (McSteen and Hake, 2001; Barazesh and McSteen, 2008; Skirpan et al., 2009). Ectopicexpression of TAPETUM DETERMINANT1 (TPD1) causes abnormal ovule and seed development viaaltering auxin signaling (Huang et al., 2016b,c. The rice gene LAZY1 (LA1), which encodes a novelgrass specific protein, is a negative regulator of polar auxin transport (Li et al., 2007).
Spikeletsin la1-ref (La1 orthologue) either are not fully developed orundergo abortion in the tassel tip.
