Genome-wide analysis of maize NLP transcription factor family revealed the roles in nitrogen response

Abstract

NIN-LIKE PROTEIN (NLP) is a conserved plant-specific transcription factor family and has been shown in several plant species to be a key player in regulating nitrogen (N) response. However, little is known about NLP gene family and their characteristics in maize (Zea mays L.). Here we report the identification and characterization of maize NLPs (ZmNLPs), and illustrate the family structure, phylogenetic properties, expression profiles, genetic differentiation between heterotic groups and N response. A total of 9 ZmNLPs from the maize genome were identified, belonging to two subgroups according to conserved domains and gene structure. Their expression profiles were different across tissues and almost all ZmNLPs constitutively expressed in eight different tissues at various developmental stages. Three ZmNLPs (ZmNLP3, 5 and 9) implementing the F ST higher than 0.25, differentiated very greatly between the Iowa Stiff Stalk Synthetic (SS) and Non-Stiff Stalk (NSS) heterotic groups. Quantitative real-time PCR (qPCR) results showed the expression levels of four ZmNLPs (ZmNLP4, 5, 6 and 8) were up-regulated over twofold in response to N treatment, ZmNLP4 and ZmNLP5 showed the largest up-regulation of greater than fivefold at 0.5 h after treatment which was even higher than the benchmark N-responsive gene (ZmNRT2.2) at the same time point, suggesting that they can be involved in the primary nitrogen response. As the first effort aimed to identify and characterize NLP transcription factor gene family in maize, our study also indicates ZmNLPs may have significant roles in maize N response.