Abstract
BackgroundThe MADS-box transcription factors mainly function in floral organ organogenesis and identity specification. Few research on their roles in vegetative growth has been reported.ResultsHere we investigated the functions of OsMADS57 in plant vegetative growth in rice (Oryza sativa). Knockdown of OsMADS57 reduced the plant height, internode elongation and panicle exsertion in rice plants. Further study showed that the cell length was remarkably reduced in the uppermost internode in OsMADS57 knockdown plants at maturity. Moreover, OsMADS57 knockdown plants were more sensitive to gibberellic acid (GA3), and contained less bioactive GA3 than wild-type plants, which implied that OsMADS57 is involved in gibberellin (GA) pathway. Expectedly, the transcript levels of OsGA2ox3, encoding GAs deactivated enzyme, were significantly enhanced in OsMADS57 knockdown plants. The level of EUI1 transcripts involved in GA deactivation was also increased in OsMADS57 knockdown plants. More importantly, dual-luciferase reporter assay and electrophoretic mobility shift assay showed that OsMADS57 directly regulates the transcription of OsGA2ox3 as well as EUI1 through binding to the CArG-box motifs in their promoter regions. In addition, OsMADS57 also modulated the expression of multiple genes involved in GA metabolism or GA signaling pathway, indicating the key and complex regulatory role of OsMADS57 in GA pathway in rice.ConclusionsThese results indicated that OsMADS57 acts as an important transcriptional regulator that regulates stem elongation and panicle exsertion in rice via GA-mediated regulatory pathway.
Highlights
The MADS-box transcription factors mainly function in floral organ organogenesis and identity specification
In the GA biosynthetic pathway, geranylgeranyl diphosphate is converted to ent-kaurene, which is catalyzed by ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase (KS) (Helmut Aach et al 1997)
OsMADS57 alters the transcription of genes involved in GA metabolism To determine whether the inhibition of internode elongation in m57–2 and m57–1 plants is caused by reduced contents of bioactive GAs, we firstly investigated the expression of genes encoding GA metabolic enzymes by quantitative PCR (Q-PCR) analysis
Summary
The MADS-box transcription factors mainly function in floral organ organogenesis and identity specification. In “Green Revolution”, high-yielding cultivars have been created that have suitable height in rice and wheat (Khush 2001; Thomas et al 2005). Both the improved lodging resistance and increased total biomass result from their short stature (Sakamoto and Matsuoka 2004). In the GA biosynthetic pathway, geranylgeranyl diphosphate is converted to ent-kaurene, which is catalyzed by ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase (KS) (Helmut Aach et al 1997). With the catalysis of two cytochrome P450 enzymes, ent-kaurene oxidase (KO) and ent-kaurenoic acid oxidase (KAO), ent-kaurene is converted to GA12 (Helliwell et al 2001). CYP714B1 and CYP714B2, two cytochrome P450 genes, encode GA 13-oxidase that is responsible for converting GA12 to GA53,
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