Nitrogen regulatory networks controlling flowering time in Arabidopsis thaliana

GRAS DE; MANCILLA Y; VIDAL EA; GUTIÉRREZ RA

Pucón - Región de Araucanía

Encuentro; VI Reunión de Biología Vegetal; 2011

Sociedad de Biología Vegetal

Nitrogen (N) is an essential macronutrient and its availability is one of the primary factors limiting plant growth and agricultural productivity. N nutrient/metabolites can have profound impact on root development, flowering time and other developmental programs. Some of the regulatory gene networks mediating root developmental responses to N availability have been identified. However, despite the economic importance of understanding the relationship between plant N nutrition and flowering, relatively little is known about the molecular mechanisms that control flowering time in response to N supply. To investigate how plants sense and respond to N at the molecular level to coordinate flowering time, we integrated known floral gene networks with N-networks obtained from public databases. Our systems analysis identified important floral genes regulated by N. Among them, several repressors of flowering time are regulated by nitrate including, two TARGET OF EAT 1 and 2 (TOE1 and TOE2, respectively), SCHLAFMUTZE (SMZ) and SCHNARCHZAPFEN (SNZ). These genes are targets of microRNA172 (miR172), a regulatory factor that controls flowering time by the photoperiod pathway. To analyze the possible role of these transcription factors in the N-response, we evaluated the effect of nitrate treatments on the expression of these genes. TOE1, TOE2, SMZ and SNZ RNA accumulated quickly after KNO3 treatments but not after KCl treatments (as control) indicating they are nitrate responsive genes. We also found that miR172 was down regulated by nitrate treatments. To understand the functional role of this N-regulatory module for plant development, we analyzed the flowering time response to nitrate in toe1,toe2, smz and snz insertional mutants and in miR172 overexpressor lines. Our work defined a model for N control of flowering time in Arabidopsis thaliana that involves miR172 and their targets SNZ and SMZ.