Regulatory role of FZP in the determination of panicle branching and spikelet formation in rice

Abstract

FRIZZLE PANICLE (FZP) and RFL/ABERRANT PANICLE ORGANIZATION 2 (APO2) play important roles in regulating the ABCDE floral organ identity genes. However, the relationships among FZP and these floral identity genes in the regulation of panicle formation remain unclear. Here, we used the novel mutant fzp-11, wild-type and FZP-overexpressing plants to compare the expression of these genes during panicle development by real-time PCR and in situ hybridization. The results indicate that FZP is a major negative regulator of RFL/APO2 and determines the transition from panicle branching to spikelet formation. Moreover, overexpression of FZP severely represses axillary meristem formation in both the vegetative and reproductive phases and the outgrowth of secondary branches in panicle. FZP overexpression positively regulates the expression of a subset of the class B genes, AGL6 genes (OsMADS6 and OsMADS17) as well as class E genes (OsMADS1, OsMADS7 and OsMADS8) in floral meristem (FM). Thus, it suggested that FZP could specify floral organ identity by regulating the related OsMADS-box genes.

Grass inflorescence architecture and evolution: the origin of novel signaling centers

“…Similar mutants have been described more recently in barley, wheat and Brachypodium distachyon (Derbyshire & Byrne, 2013;Poursarebani et al, 2015). Overexpression of FZP has the opposite effect of a fzp mutant, inducing precocious spikelet identity and reducing indeterminate branching (Bai et al, 2016).…”

“…Similar mutants have been described more recently in barley, wheat and Brachypodium distachyon (Derbyshire & Byrne, ; Poursarebani et al ., ). Overexpression of FZP has the opposite effect of a fzp mutant, inducing precocious spikelet identity and reducing indeterminate branching (Bai et al ., ). Although the ectopic production of axillary buds from the glumes indicates a loss of SM identity, it is important to note that spikelet identity is not fully lost as other aspects of glume identity are maintained in bd1/fzp mutants.…”

Systems model‐guided rice yield improvements based on genes controlling source, sink, and flow

“…FZP is a major negative regulator of RFL/APO2 , which mediates in the transition from panicle branching to spikelet formation (Komatsu et al ). Overexpression of FZP represses axillary bud formation in both vegetative and reproductive phases (Bai et al ). Recently, a silencer was discovered, which is an 18‐bp DNA sequence located 5.3 kb upstream of the FZP initiation codon that can regulate FZP expression.…”

“…The large glume covering a floret is called the lemma and the smaller one is referred to as the palea. Grain weight is generally controlled by grain cell division and the degree of grain filling, whereas tiller number and floret number per panicle are determined by lateral branch development, during both the vegetative and reproductive growth stages (Wang 2015;Huang et al 2016). These three components of sink strength constrain each other; for example, tiller number and floret number per panicle are usually negatively correlated to each other; similarly, there is a negative correlation between grain size and floret number (Hu 2011).…”

Short Panicle 3 controls panicle architecture by upregulating APO2/RFL and increasing cytokinin content in rice

“…In the role of main regulators of axillary meristem formation and activity maintenance, LAX PANICLE 1 ( LAX1 ), LAX2 and MONOCULM 1 ( MOC1 )/ SMALL PANICLE ( SPA ) positively regulate panicle branching (Komatsu et al ; Oikawa and Kyozuka ; Tabuchi et al ). By contrast, FRIZZY PANICLE ( FZP ) represses panicle branching in an action opposite to that of LAX1 (Komatsu et al ; Bai et al ). Finally, Ghd7 , Ghd7.1 and Ghd8 regulate not only panicle length but also the number of primary and secondary branches (Xue et al ; Yan et al ; Yan et al ).…”