Abstract
BackgroundFPF1 (flowering-promoting factor 1) is one of the important family involved in the genetic control of flowering time in plant. Until now, limited knowledge concerning FPF1 family in rice has been understood.ResultsAs a homologue of AtFPF1, FPF1-like protein 4 of rice (OsFPFL4) is expressed in various tissues of plants. The functions of OsFPFL4 in rice were investigated by the reverse genetics approaches. Plants overexpressing OsFPFL4 have shorter primary root, more lateral roots and adventitious roots than wild type; however, RNA interference (RNAi) of OsFPFL4 significantly inhibits the growth of root system, and also delays the flowering time in rice. Interestingly, increased or repressed expression of OsFPFL4 leads to shrunken anthers and abnormal pollen grains. It is well recognized that auxin plays important roles in plant root and flower development, and the root elongation is also regulated by reactive oxygen species (ROS) homeostasis. Here, our results show that rice plants overexpressing OsFPFL4 accumulate more auxin in the shoot and root, whereas RNAi lines have less auxin than wild type. As expected, the transcript levels of genes responsible for auxin biosynthesis and polar transport are altered in these OsFPFL4 transgenic plants. As to ROS, slightly higher ROS levels were detected in overexpression root and inflorescence than the counterparts of wild type; however, the ROS levels were significantly increased in the RNAi lines, due to increased expression of ROS-producers and reduced expression of ROS-scavengers.ConclusionOur results reveal that OsFPFL4 is involved in modulating the root and flower development by affecting auxin and ROS homeostasis in rice plants. OsFPFL4 controls auxin accumulation via affecting auxin biosynthesis and transport, and also modulates ROS homeostasis by balancing ROS producing and scavenging. Thus, auxin-mediated ROS production might play a role in regulating redox status, which controls plant root and flower development.
Highlights
FPF1 is one of the important family involved in the genetic control of flowering time in plant
FPF1 homologues indicated OsFPFL4 was located in a branch close to OsRAA1, but far from AtFPF1 (Fig. 1b), implying that OsFPFL4 might have functions similar to that of OsRAA1 in plant growth and development
OsFPFL4 mRNA preferentially accumulated in the leaf blade and root at the seedling as well as tillering stages; at the heading stage, transcripts of OsFPFL4 peaked in the inflorescence, and only small quantities of transcripts accumulated in the leaf blade and leaf sheath (Fig. 2a)
Summary
FPF1 (flowering-promoting factor 1) is one of the important family involved in the genetic control of flowering time in plant. Endogenous auxin biosynthesis, polar transport, and degradation/conjugation can change its accumulation and auxin-dependent signaling (Petricka et al 2012; Lavenus et al 2013), and mutations involved in these processes significantly affect the lateral root development (Fukaki and Tasaka 2009; Peret et al 2009). Gain-of-function mutants such as yucca1-D, sur, and sur with increased auxin levels produce more lateral roots (Zhao et al 2001; Peret et al 2009). Mutants with altered auxin transport, such as Arabidopsis aux, lax, pin, pin 3/7, pin 4/7 and rice osaux have less lateral roots (Benkova et al 2003; Peret et al 2009; Zhao et al 2015)
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