Overexpression of miR169o, an Overlapping MicroRNA in Response to Both Nitrogen Limitation and Bacterial Infection, Promotes Nitrogen Use Efficiency and Susceptibility to Bacterial Blight in Rice

Abstract

Limiting nitrogen (N) supply contributes to improved resistance to bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) in susceptible rice (Oryza sativa). To understand the regulatory roles of microRNAs (miRNAs) in this phenomenon, 63 differentially expressed overlapping miRNAs in response to Xoo infection and N limitation stress in rice were identified through deep RNA sequencing and stem-loop quantitative real-time PCR. Among these, miR169o was further assessed as a typical overlapping miRNA through the overexpression of the miR169o primary gene. Osa-miR169o-OX plants were taller, and had more biomass accumulation with significantly increased nitrate and total amino acid contents in roots than the wild type (WT). Transcript level assays showed that under different N supply conditions, miR169o oppositely regulated NRT2, and this is reduced under normal N supply conditions but remarkably induced under N-limiting stress. On the other hand, osa-miR169o-OX plants also displayed increased disease lesion lengths and reduced transcriptional levels of defense gene (PR1b, PR10a, PR10b and PAL) compared with the WT after inoculation with Xoo. In addition, miR169o impeded Xoo-mediated NRT transcription. Therefore, the overlapping miR169o contributes to increase N use efficiency and negatively regulates the resistance to BB in rice. Consistently, transient expression of NF-YA genes in rice protoplasts promoted the transcripts of PR genes and NRT2 genes, while it reduced the transcripts of NRT1 genes. Our results provide novel and additional insights into the co ordinated regulatory mechanisms of cross-talk between Xoo infection and N deficiency responses in rice.

Characteristic Dissection of Xanthomonas oryzae pv. oryzae Responsive MicroRNAs in Rice

“…Recent reports on miRNAs in rice-Xoo interaction were mostly sequencing-based, and the samples were collected from single less-resistant genotype or/and its transgenic resistant derivatives [28,29,32]. To exclude the limitation of single material and the unpredictable impact of transgenic approach and resistant gene, the rice accessions IR24 and IRBB5 were chosen to construct small RNA libraries for investigate the regulatory roles of miRNAs because of no miRNA targeting the Xoo-resistant gene xa5 in bioinformatic analysis (http://plantgrn.noble.org/v1_psRNATarget/).…”

“…Moreover, osa-mi319/OsTCP21 [27], osa-miR444/OsMADS57 [26], osa-miR171b/OsSCL6-IIa, OsSCL6-IIb, OsSCL6-IIc [25] and osa-miR528/OsAO [24] regulatory units could change the disease development caused by rice stripe virus and rice ragged stunt virus, respectively. However, only two regulatory units, osa-miR156/OsIPA1 [31] and osa-miR169o/OsNF-YA [32], were published, which mediated immunity to Xoo. Integrating analysis of small RNA sequencing and degradome data showed that 29 DE known miRNAs might be involved in anti-bacterial regulatory mechanism in BB.…”

“…The inducible knockdown of osa-miR156 could motivate OsIPA1 expression, to debar the fitness penalty of BB resistance in rice [31]. Conversely, the enhancive osa-miR169o boosted the pathogenicity of Xoo strains [32].…”

Rice siR109944 suppresses plant immunity to sheath blight and impacts multiple agronomic traits by affecting auxin homeostasis

“…Many studies have reported that miRNAs are associated with rice immune responses against pathogens such as Magnaporthe oryzae ( M. oryzae ) (Li et al , , ; Wang et al , ; Zhang et al , ), Rice ragged stunt virus (RRSV) (Zhang et al , ), rice stripe virus (RSV) (Wu et al , ), and Xanthomonas oryzae pv. oryzae ( Xoo ) (Zhao et al , ; Yu et al , ). For example, overexpression of miR160a and miR398b in transgenic rice plants enhanced rice blast resistance by increasing hydrogen peroxide accumulation at the infection site and upregulating the expression of defence‐related genes (Li et al , ).…”

“…For example, overexpression of miR160a and miR398b in transgenic rice plants enhanced rice blast resistance by increasing hydrogen peroxide accumulation at the infection site and upregulating the expression of defence‐related genes (Li et al , ). Moreover, the miR169 family negatively regulates rice immunity against M. oryzae and Xoo by differentially repressing the expression of its target genes, the nuclear factor Y ‐ A ( NF‐YA ) family members (Li et al , ; Yu et al , ). In addition, miR319‐ mediated regulation of OsTCP21 might affect rice resistance against blast disease and RRSV infection by manipulating jasmonic acid (JA) signalling (Zhang et al , , ).…”