AP2/DREB Transcription Factor RAP2.4 Activates Cuticular Wax Biosynthesis in Arabidopsis Leaves Under Drought

Abstract

Drought is a critical environmental stress that limits growth and development of plants and reduces crop productivity. The aerial part of land plants is covered with cuticular waxes to minimize water loss. To understand the regulatory mechanisms underlying cuticular wax biosynthesis in Arabidopsis under drought stress conditions, we characterized the role of an AP2/DREB type transcription factor, RAP2.4. RAP2.4 expression was detected in one-week-old seedlings and rosette leaves, stems, stem epidermis, cauline leaves, buds, flowers, and siliques of 6-week-old Arabidopsis. The levels of RAP2.4 transcripts increased with treatments of abscisic acid (ABA), mannitol, NaCl, and drought stress. Under drought, total wax loads decreased by approximately 11% and 10%, and in particular, the levels of alkanes, which are a major wax component, decreased by approximately 11% and 12% in rap2.4-1 and rap2.4-2 leaves, respectively, compared with wild type (WT) leaves. Moreover, the transcript levels of cuticular wax biosynthetic genes, KCS2 and CER1, decreased by approximately 15-23% and 32-40% in rap2.4-1 and rap2.4-2 leaves, respectively, relative to WT 4 h after drought treatment, but increased by 2-to 12-fold and 3-to 70-fold, respectively, in three independent RAP2.4 OX leaves relative to WT. Epicuticular wax crystals were observed on the leaves of RAP2.4 OX plants, but not on the leaves of WT. Total wax loads increased by 1.5-to 3.3-fold in leaves of RAP2.4 OX plants relative to WT. Cuticular transpiration and chlorophyll leaching occurred slowly in the leaves of RAP2.4 OX plants relative to WT. Transcriptional activation assay in tobacco protoplasts showed that RAP2.4 activates the expression of KCS2 and CER1 through the involvement of the consensus CCGAC or GCC motifs present in the KCS2 and CER1 promoter regions. Overall, our results revealed that RAP2.4 is a transcription factor that activates cuticular wax biosynthesis in Arabidopsis leaves under drought stress conditions.

Genome-Wide Identification of the AP2/ERF Gene Family and Functional Analysis of GmAP2/ERF144 for Drought Tolerance in Soybean

“…Transcription factors contain one or more specific DNA-binding domains and are essential in regulating gene expression throughout the life cycles of higher plants ( Hao et al, 1998 ). The AP2/ERF (APETALA2/ethylene-responsive element binding factors) TFs are a large group that is mainly found in plants ( Yang S. U. et al, 2020 ). The TFs of this family are important regulators of many biological and physiological processes, including plant morphogenesis, responses to various stresses, hormone signal transduction, and biosynthesis of metabolites ( Feng et al, 2020 ).…”

Different Functions of IbRAP2.4, a Drought-Responsive AP2/ERF Transcription Factor, in Regulating Root Development Between Arabidopsis and Sweetpotato

“…DREBs have been extensively examined under abiotic stress, where they respond to and positively regulated drought, cold, salt, and heat tolerance by regulating stress-responsive genes ( Xie et al, 2019 ). Drought- and salt- inducible Arabidopsis RAP2.4 is reported to regulate multiple developmental processes and drought stress tolerance ( Lin et al, 2008 ; Yang et al, 2020 ). In this study, IbRAP2.4 expression was highly detected in sweetpotato roots ( Figure 2A ), and induced by treatments of salinity, dehydration, ethylene, and IAA ( Figure 2B ).…”

Advancement of Metatranscriptomics towards Productive Agriculture and Sustainable Environment: A Review

“…It was shown that the upregulated genes due to B. cinera infection, which include CCR2 , CYP71A13 , NATA1 , SRG1 , and EL13-2 , are responsive to phytohormones (salicylic acid, methyl-jasmonate, 1-aminoacyclopropane-1-carboxylate, and abscisic acid), indicating that hormones play a dominant role in the transcriptional programming of the Arabidopsis defence response towards B. cinera infection. Alongside that, the potential of the RAP2.4 gene to serve in plant defence by regulating endogenous signal molecules and pathogen-derived effectors was also highlighted, whereas previous research had reported a similar elevation in gene expression under drought stress [ 75 ]. Thus, the information of the DEGs in response to plant infection makes it possible to understand the mechanisms underlying the plant defence system, which can subsequently be utilised to develop disease-suppressive soils and enable genetic modification of the crop with the desired defensive traits.…”