Abstract
Senescence is the final stage of leaf development which is accompanied by highly coordinated and complicated reprogramming of gene expression. Genetic manipulation of leaf senescence in major crops including wheat has been shown to be able to increase stress tolerance and grain yield. NAC(No apical meristem (NAM), ATAF1/2, and cup-shaped cotyledon (CUC)) transcription factors (TFs) play important roles in regulating gene expression changes during leaf senescence and in response to abiotic stresses. Here, we report the characterization of TaSNAC11-4B (Uniprot: A0A1D5XI64), a wheat NAC family member that acts as a functional homolog of AtNAP, a key regulator of leaf senescence in Arabidopsis. The expression of TaSNAC11-4B was up-regulated with the progression of leaf senescence, in response to abscisic acid (ABA) and drought treatments in wheat. Ectopic expression of TaSNAC11-4B in Arabidopsis promoted ROS accumulation and significantly accelerated age-dependent as well as drought- and ABA-induced leaf senescence. Results from transcriptional activity assays indicated that the TaSNAC11-4B protein displayed transcriptional activation activities that are dependent on its C terminus. Furthermore, qRT-PCR and dual-Luciferase assay results suggested that TaSNAC11-4B could positively regulate the expression of AtrbohD and AtrbohF, which encode catalytic subunits of the ROS-producing NADPH oxidase. Further analysis of TaSNAC11-4B in wheat senescence and the potential application of this gene in manipulating leaf senescence with the purpose of yield increase and stress tolerance is discussed.
Highlights
The leaf is the main photosynthetic organ for the production of energy during plant development and the status of leaves is essential for the efficiency of photosynthesis [1]
The results indicated a significant increase in TaSNAC11-4B expression at early stages of leaf senescence (Figure 1A)
Given that NAP transcription factors (TFs) as well as a number of other NAC TF family members have been shown to be involved in stress responses [27,35,52,53], we examined the expression of TaSNAC11-4B in detached leaves after treatment with phytohormones abscisic acid (ABA), MeJA, 1-aminocyclopropane-1-carboxylic acid (ACC), salicylic acid (SA), indole-3-aceticacid (IAA), and stressors including NaCl and drought (PEG6000 mimic)
Summary
The leaf is the main photosynthetic organ for the production of energy during plant development and the status of leaves is essential for the efficiency of photosynthesis [1]. Appropriate maintenance of the productive photosynthetic stage is essential to crop yield [2]. The leaf senescence process is critical in the recycling and reallocation of nutrients from vegetative to reproductive tissues to promote seed production and to ensure plants’ survival under harsh environmental conditions [5,6]. The timing of leaf senescence is crucial for crop production. Senescence could reduce plants’ capacity for carbon assimilation and nitrogen uptake, while over-delayed senescence could cause plants to miss the best time for remobilizing nutrients to reproductive organs [5,7]
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