NAC transcription factor family genes are differentially expressed in rice during infections with Rice dwarf virus, Rice black-streaked dwarf virus, Rice grassy stunt virus, Rice ragged stunt virus, and Rice transitory yellowing virus.

Mohammed Nuruzzaman,Takahide Sasaya,Kouji Satoh,Takumi Shimizu,Mohammad Rezaul Karim,Shoshi Kikuchi,Mohammad A Haque,Sayed M Z Hasan,Aziz Ahmad,Akhter M Sharoni,Jennifer A Harikrishna,Toshihiro Omura

doi:10.3389/fpls.2015.00676

Abstract

Expression levels of the NAC gene family were studied in rice infected with Rice dwarf virus (RDV), Rice black-streaked dwarf virus (RBSDV), Rice grassy stunt virus (RGSV), Rice ragged stunt virus (RRSV), and Rice transitory yellowing virus (RTYV). Microarray analysis showed that 75 (68%) OsNAC genes were differentially regulated during infection with RDV, RBSDV, RGSV, and RRSV compared with the control. The number of OsNAC genes up-regulated was highest during RGSV infection, while the lowest number was found during RTYV infection. These phenomena correlate with the severity of the syndromes induced by the virus infections. Most of the genes in the NAC subgroups NAC22, SND, ONAC2, ANAC34, and ONAC3 were down-regulated for all virus infections. These OsNAC genes might be related to the health stage maintenance of the host plants. Interestingly, most of the genes in the subgroups TIP and SNAC were more highly expressed during RBSDV and RGSV infections. These results suggested that OsNAC genes might be related to the responses induced by the virus infection. All of the genes assigned to the TIP subgroups were highly expressed during RGSV infection when compared with the control. For RDV infection, the number of activated genes was greatest during infection with the S-strain, followed by the D84-strain and the O-strain, with seven OsNAC genes up-regulated during infection by all three strains. The Os12g03050 and Os11g05614 genes showed higher expression during infection with four of the five viruses, and Os11g03310, Os11g03370, and Os07g37920 genes showed high expression during at least three viral infections. We identified some duplicate genes that are classified as neofunctional and subfunctional according to their expression levels in different viral infections. A number of putative cis-elements were identified, which may help to clarify the function of these key genes in network pathways.

Highlights

The NAC gene family name was derived from the names of three transcription factors: NAM, ATAF1–2 (Arabidopsis thaliana activating factor), and CUC2, which share the same DNA-binding domain (Souer et al, 1996; Aida et al, 1997)
We investigated the expression of NAC family genes in seedlings and compared OsNAC gene expression during infection with three strains of Rice dwarf virus (RDV-D84, -O, and -S), Rice black-streaked dwarf virus (RBSDV), Rice grassy stunt virus (RGSV), Rice ragged stunt virus (RRSV), and Rice transitory yellowing virus (RTYV) on different days post-inoculation
Disease Symptoms Caused by Different Virus Infections In this study, we used five viruses mentioned in methods: RDV-infected plants at 21 dpi; RBSDV, RGSV, and RRSVinfected plants at 28 dpi; and RTYV-infected plants at 24 dpi, respectively (Figure 1)

Summary

Introduction

The NAC gene family name was derived from the names of three transcription factors: NAM (no apical meristem, Petunia), ATAF1–2 (Arabidopsis thaliana activating factor), and CUC2 (cup-shaped cotyledon, Arabidopsis), which share the same DNA-binding domain (Souer et al, 1996; Aida et al, 1997). In recent years there has been improved knowledge on the molecular mechanisms underlying signaling pathways (Liu et al, 2010) and their involvement in activating defense responses in rice (Valent and Khang, 2010) and of rice innate immune responses, host recognition of pathogens (Skamnioti and Gurr, 2009) and recognition-triggered early signaling events. Several studies have elucidated the mechanisms that regulate the innate immune response in rice blast disease (i.e., OsNAC111) during infection by Magnaporthe oryzae (Yokotani et al, 2014), leading to the characterization of multiple disease resistance genes (R genes) (Liu et al, 2010). The role of NAC genes in plant responses to abiotic stresses such as drought, salinity, cold, and submergence have been widely reported (Hegedus et al, 2003; Hu et al, 2006, 2008; Jeong et al, 2010; Nuruzzaman et al, 2012b; Sun et al, 2015)

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Results

Conclusion