Foxtail Millet NF-Y Families: Genome-Wide Survey and Evolution Analyses Identified Two Functional Genes Important in Abiotic Stresses.

Zhao-Shi Xu,Wei-Jun Zheng,Guan-Hua He,Pan-Pan Lu,Zhi-Juan Feng,Ming Chen,You-Zhi Ma,Ya-Ming Gong

doi:10.3389/fpls.2015.01142

Abstract

It was reported that Nuclear Factor Y (NF-Y) genes were involved in abiotic stress in plants. Foxtail millet (Setaria italica), an elite stress tolerant crop, provided an impetus for the investigation of the NF-Y families in abiotic responses. In the present study, a total of 39 NF-Y genes were identified in foxtail millet. Synteny analyses suggested that foxtail millet NF-Y genes had experienced rapid expansion and strong purifying selection during the process of plant evolution. De novo transcriptome assembly of foxtail millet revealed 11 drought up-regulated NF-Y genes. SiNF-YA1 and SiNF-YB8 were highly activated in leaves and/or roots by drought and salt stresses. Abscisic acid (ABA) and H2O2 played positive roles in the induction of SiNF-YA1 and SiNF-YB8 under stress treatments. Transient luciferase (LUC) expression assays revealed that SiNF-YA1 and SiNF-YB8 could activate the LUC gene driven by the tobacco (Nicotiana tobacam) NtERD10, NtLEA5, NtCAT, NtSOD, or NtPOD promoter under normal or stress conditions. Overexpression of SiNF-YA1 enhanced drought and salt tolerance by activating stress-related genes NtERD10 and NtCAT1 and by maintaining relatively stable relative water content (RWC) and contents of chlorophyll, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and malondialdehyde (MDA) in transgenic lines under stresses. SiNF-YB8 regulated expression of NtSOD, NtPOD, NtLEA5, and NtERD10 and conferred relatively high RWC and chlorophyll contents and low MDA content, resulting in drought and osmotic tolerance in transgenic lines under stresses. Therefore, SiNF-YA1 and SiNF-YB8 could activate stress-related genes and improve physiological traits, resulting in tolerance to abiotic stresses in plants. All these results will facilitate functional characterization of foxtail millet NF-Ys in future studies.

Highlights

MATERIALS AND METHODSNuclear Factor Y (NF-Y), called heme-activated protein (HAP) or CCAAT binding factor (CBF), is a heterotrimeric transcription factor comprised of three distinct subunits: NF-YA (HAP2 or CBF-B), NF-YB (HAP3 or CBF-A), and NF-YC (HAP5 or CBF-C) (Romier et al, 2003)
Similar to SiNF-YA1, fluridone and dimethyl thiourea (DMTU) had no effect on the expression of SiNF-YB8 (Supplementary Figure S4B); and pretreatment with Abscisic acid (ABA) and H2O2 inhibitors prevented up-regulation of SiNF-YB8 in PEG- and mannitol-treated foxtail millet seedlings (Figure 6B). These results suggested that ABA and H2O2 were involved in up-regulation of SiNF-YA1 and SiNF-YB8 under PEG, NaCl or mannitol treatment, respectively
Previous studies demonstrated that NF-Y transcription factor genes played important roles in abiotic stress (Nelson et al, 2007; Stephenson et al, 2007; Han et al, 2013; Ni et al, 2013)

Summary

Introduction

MATERIALS AND METHODSNuclear Factor Y (NF-Y), called heme-activated protein (HAP) or CCAAT binding factor (CBF), is a heterotrimeric transcription factor comprised of three distinct subunits: NF-YA (HAP2 or CBF-B), NF-YB (HAP3 or CBF-A), and NF-YC (HAP5 or CBF-C) (Romier et al, 2003). Three independent transgenic tobacco lines with higher expression of target gene were used to perform abiotic stress tolerance assay. Transcription activity of SiNF-YA1 or SiNF-YB8 against promoters of stress responsive marker genes was performed using dual luciferase assay of transiently transformed tobacco leaves (Huang et al, 2013).

Results

Conclusion