Cowpea NAC1/NAC2 transcription factors improve growth and tolerance to drought and heat in transgenic cowpea through combined activation of photosynthetic and antioxidant mechanisms

Abstract

NAC (NAM/ATAF1/2/CUC2) transcription factors are central switches of growth and stress responses in plants. However, unpredictable interspecies conservation of function and regulatory targets makes the well-studied NAC orthologs inapt for pulse engineering. The knowledge of suitable NAC candidates in hardy pulses like cowpea (Vigna unguiculata (L.) Walp.) is still in infancy, hence warrants immediate biotechnological intervention. Here, we showed that overexpression of two native NAC genes (VuNAC1 and VuNAC2) promoted germinative, vegetative, and reproductive growth and conferred multiple abiotic stress tolerance in a commercial cowpea variety. The transgenic lines displayed increased leaf area, thicker stem, nodule-rich denser root system, early flowering, higher pod production (∼3.2-fold and ∼2.1-fold), and greater seed weight (10.3% and 6.0%). In contrast, transient suppression of VuNAC1/2 caused severe growth retardation and flower inhibition. The overexpressor lines showed remarkable tolerance to major yielddeclining terminal stresses, such as drought, salinity, heat, and cold, and recovered growth and seed production by boosting photosynthetic activity, water use efficiency, membrane integrity, Na + /K + homeostasis, and antioxidant activity. The comparative transcriptome study indicated consolidated activation of genes involved in chloroplast development, photosynthetic complexes, cell division and expansion, cell wall biogenesis, nutrient uptake and metabolism, stress response, abscisic acid, and auxin signaling. Unlike their orthologs, VuNAC1/2 direct synergistic transcriptional tuning of stress and developmental signaling to avoid unwanted trade-offs. Their overexpression governs the favorable interplay of photosynthesis and reactive oxygen species regulation to improve stress recovery, nutritional sufficiency, biomass, and production. This unconventional balance of strong stress tolerance and agronomic quality is useful for translational crop research and molecular breeding of pulses.

How plants sense and respond to osmotic stress

“…Except for ABA receptors, all the core signaling components of ABA signaling, including PP2Cs, SnRK2s, basic region/leucine zipper motif (bZIP) transcription factors, and ion channels SLAC1, are present in green algae and shared with hyperosmotic stress signaling in terrestrial plants (Hauser et al, 2011; Wang et al, 2015a; Sun et al, 2019). Besides bZIPs, other transcription factors also contribute to drought stress (Song et al, 2016; Wang et al, 2022b; Li et al, 2023b; Srivastava et al, 2023; Wei et al, 2023). The common ancestor of terrestrial plants and Zygnematophyceae gain the basal ABA‐independent pre‐PYL to hijack the osmotic stress signaling in algae and, in turn, the common ancestor of land plants has evolved ABA‐dependent PYLs, the ABA receptors (de Vries et al, 2018; Cheng et al, 2019; Sun et al, 2019).…”

NAC1 transcriptional activation of LDHA induces hepatitis B virus immune evasion leading to cirrhosis and hepatocellular carcinoma development

“…NAC1, a crucial molecular regulatory factor, has shown significance in diverse cancers, specifically in the proliferation, invasion, and migration of cancer cells [ 32 ]. Abnormal expression of NAC1 is strongly correlated with the progression of diseases and unfavorable prognosis in other types of cancer [ 16 ].…”

Plant biomarkers as early detection tools in stress management in food crops: a review

“…The resulting transgenic plants displayed enhanced antioxidant activity, membrane integrity, water use efficiency, and Na + /K + balance. These improvements culminated in an estimated threefold increase in growth and yield, (Srivastava et al 2023 ).…”