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DWARF 3 (D3), an F-box component of the SKP?Cullin?F box (SCF) E3 ubiquitin ligase complex, is a suppressor of LAZY1. D3 regulates shoot gravitropism independent of LAZY1. D3 expression is not affected in lazy1 mutant, and the expression of LAZY1 remains unchanged in d3 seedlings. Indeed, D3 and LAZY1 have parallel but opposite functions in regulating shoot gravitropism through an asymmetric auxin distribution (Sang et al., 2014). Strigolactones inhibit auxin biosynthesis and attenuate rice shoot gravitropism primarily by decreasing local indoleacetic acid (IAA) contents. D3 is involved in strigalactone signaling pathways (Zhao et al., 2014). Thus, down-regulation of D3 leads to increased levels of auxins and enhanced negative shoot gravitropism and rescues the spreading phenotype of lazy1 mutant (Sang et al., 2014).
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