PvNAC1 and PvNAC2 Are Associated with Leaf Senescence and Nitrogen Use Efficiency in Switchgrass

Abstract

Two full-length cDNAs encoding NAM, ATAF, and CUC (NAC)-family transcription factors (TFs) were isolated from two different cultivars of Panicum virgatum L. (switchgrass) and named PvNAC1 and PvNAC2. Phylogenetic analysis of PvNAC1 and PvNAC2 grouped them with NAC proteins involved in senescence in annual plant species. Transcript profiling revealed that both PvNAC1 and PvNAC2 are induced during leaf senescence. Expression of a PvNAC1-green fluorescent protein (GFP) fusion in plant cells revealed a nuclear location of the protein, consistent with a role in transcriptional regulation. Expression of PvNAC1 in an Arabidopsis nap stay-green mutant suppressed its senescence defect. Expression of PvNAC1 in wild-type Arabidopsis triggered early leaf senescence and remobilization. Transcriptome analysis implicated leaf protein degradation and nitrogen recycling enzymes in NAC-dependent seed protein increase in Arabidopsis. Overexpression of pvNAC2 in switchgrass resulted in increased aboveground biomass associated with increased transcript levels of key nitrogen metabolism genes in leaves and nitrate and ammonium transporter genes in roots. The results indicate that NAC TFs play conserved roles in leaf senescence in the plant kingdom not only in annual monocots and dicots but also in perennial plants such as switchgrass. PvNAC1 and PvNAC2 hold promise for improving nutrient use efficiency in switchgrass through genetic manipulation.

Hydrogen sulfide and rhizobia synergistically regulate nitrogen (N) assimilation and remobilization during N deficiency‐induced senescence in soybean

“…During soybean senescence, H 2 S and rhizobia enhanced the transcription of the GmNAC1 , GmNAC3 , GmNAC4 , GmNAC5 , and GmNAC6 genes and downregulated the expression of GmNAC2 in leaves (Figure f‐k). As previously reported, PvNAC1 and PvNAC2 were expected to improve nutrient use efficiency of switchgrass by genetic manipulation (Yang et al, ). Simultaneously, the functional grouping of SAG s in switchgrass indicated that transcription and protein degradation play a crucial role in regulating plant senescence.…”

“…TFs associated with aging are also indispensable in the coordinated control of shoot senescence and effective N remobilization. As a TF family, the NAC gene family plays a conserved role in plant leaf senescence (Hollmann, Gregersen, & Krupinska, ; Yang et al, ). For example, the expression of the transcription factor HvNAC026 and serine‐type protease SCPL51 was upregulated during senescence in barley flag leaves under standard N supply (Hollmann et al, ).…”

The WRKY transcription factor family and senescence in switchgrass

“…Among these module 3 genes was a NAC transcription factor encoded by Pavir.J16651 . This specific NAC (called PvNAC1) was demonstrated to impact leaf senescence in switchgrass [ 78 ], and is most similar to AtNAC29 , which has been implicated in leaf senescence in A. thaliana [ 79 ].…”

Plant-based biofuels

“…In addition, the square footage of the biorefinery that produces the fuel can have a major impact on sustainability, impacting the transportation radius for bringing biomass from the surrounding area 31 . Growth and nutrient-use advantages are being seen through inoculation with endophytic fungi 32 , and manipulation of transcription factor genes that are important for nutrient cycling during senescence may improve nutrient-use efficiency in perennial plants such as switchgrass 33 .…”