Modulation of SPL gene expression by miR156/157

In Arabidopsis 11 out of 17 SPL genes have been suggested to be target of the similar microRNA 156/157. Based on degradome analysis, target genes for microRNA 157 include SPL 15, SPL9, SPL2, SPL11 and SPL10. SPL gene were known to express in various tissues, at different developmental stages and regulate multiple important and divergent biological processes including leaf development (Wu and Poethig 2006),  phase transition (Usami et al .,2009), flower and fruit development (Wang et al .,2995 Mannubg et al .,2006), Plant acrhitechture (Becraft et al .,1990, Jiao et al .,2010), GA signalling (Zhang et al .,2007) as well as response to copper and fungal toxin (Eriksson et al .,2004; Stone et al .,2005). Previously, Wang, et al ., 2008 demonstrated that microRNA156/157 modulates expression of SPL in leaf primordia and that SPL activity inhibits initiation of new leaves at the shoot apical meristem. Three closely related members SPL10, SPL11 and SPL2 redundantly control laminar shape at the vegetative phase (Shikata et al .,2009), whereas leaf shape is affected by two other SPL genes SPL9 and SPL15 (Usami et al .,2009). Furthermore, SPL 9 was reported to bind directly to promoter of microRNA172 gene and activates its transcription, regulating downstream APETALA2 (AP2)-like transcrioption factor TARGET OF EAT (TOE1) and TOE2 that repress adult characteristics in the leaf epidermis (Chen et al .,2010). Similarly Degradome sequence analysis showed  SPL3,SPL4 and SPL5 as potential target genes for microRNA156 in addition to SPL 15, SPL9, SPL2, SPL11, SPL10 and SPL6 which were found to be common targets between microRNA156 and microRNA157. ATSPL3, ATSPL4 and ATSPL5 regulates trichome distribution and affects the cell number and cell size in adult leaf although they do not affect leaf shape (Wu and Poethig 2006; Usami et al .,2009).