Contribution of the drought tolerance‐related Stress‐responsive NAC1 transcription factor to resistance of barley to Ramularia leaf spot

Abstract

NAC proteins are plant transcription factors that are involved in tolerance to abiotic and biotic stresses, as well as in many developmental processes. Stress-responsive NAC1 (SNAC1) transcription factor is involved in drought tolerance in barley and rice, but has not been shown previously to have a role in disease resistance. Transgenic over-expression of HvSNAC1 in barley cv. Golden Promise reduced the severity of Ramularia leaf spot (RLS), caused by the fungus Ramularia collo-cygni, but had no effect on disease symptoms caused by Fusarium culmorum, Oculimacula yallundae (eyespot), Blumeria graminis f. sp. hordei (powdery mildew) or Magnaporthe oryzae (blast). The HvSNAC1 transcript was weakly induced in the RLS-susceptible cv. Golden Promise during the latter stages of R. collo-cygni symptom development when infected leaves were senescing. Potential mechanisms controlling HvSNAC1-mediated resistance to RLS were investigated. Gene expression analysis revealed no difference in the constitutive levels of antioxidant transcripts in either of the over-expression lines compared with cv. Golden Promise, nor was any difference in stomatal conductance or sensitivity to reactive oxygen species-induced cell death observed. Over-expression of HvSNAC1 delayed dark-induced leaf senescence. It is proposed that mechanisms controlled by HvSNAC1 that are involved in tolerance to abiotic stress and that inhibit senescence also confer resistance to R. collo-cygni and suppress RLS symptoms. This provides further evidence for an association between abiotic stress and senescence in barley and the development of RLS.

Overexpression of two ATNAC3-related genes improves drought and salt tolerance in tomato (Solanum lycopersicum L.)

“…In soybean, Glycine max, GmNAC20 and GmNAC11 gene over-expression resulted in enhanced salt and freezing tolerance, and improved salt tolerance respectively (Hao et al 2011). In barley, the overexpression of HvSNAC1 gene was found to improve drought tolerance of field grown plants (Al Abdallat et al 2014) and to confer resistance to Ramularia leaf spot (McGrann et al 2014). For these reasons, such genes are considered promising targets for use in plant genetic improvement for the development of plants tolerant to adverse environmental conditions.…”

Infection strategy of Ramularia collo‐cygni and development of ramularia leaf spot on barley and alternative graminaceous hosts

“…The process that triggers the transition of Rcc from symptomless to the symptom‐causing phase remains poorly understood. Host genetic factors (McGrann et al ., , ,b) and environmental stimuli (Makepeace et al ., ; Brown & Makepeace, ; Peraldi et al ., ) appear to play important roles in the expression of RLS. The appearance of RLS symptoms is typically observed on plants late in the growing season, usually after the ear emergence (Schützendübel et al ., ; Walters et al ., ).…”

Banana fruit NAC transcription factor MaNAC5 cooperates with MaWRKYs to enhance the expression of pathogenesis‐related genes against Colletotrichum musae

“…The involvement of NAC TFs in the plant defence response to pathogens is well established (Nuruzzaman et al, 2013;Puranik et al, 2012). The expression of many NAC genes from Arabidopsis, barley, rice, wheat and grape is enhanced during diverse biotic stresses and in response to defence-related phytohormones, such as salicylic acid (SA), jasmonic acid (JA), ethylene (ET) and abscisic acid (ABA) Feng et al, 2014;Le Hénanff et al, 2013;McGrann et al, 2015;Nuruzzaman et al, 2013;Wang et al, 2015;Wu et al, 2009;Yokotani et al, 2014). Some NAC TFs may positively regulate the plant defence response by activating pathogenesis-related (PR) genes, inducing a hypersensitive response (HR) and cell death at the infection site (Nuruzzaman et al, 2013;Puranik et al, 2012;Yokotani et al, 2014); contrastingly, other NAC TFs have been regarded as negative regulators of pathogen resistance by suppressing defence-related gene expression, implying their alliance with distinct regulatory complexes (Delessert et al, 2005;Nuruzzaman et al, 2013;Puranik et al, 2012;Wang et al, 2015).…”