BrWRKY65, a WRKY Transcription Factor, Is Involved in Regulating Three Leaf Senescence-Associated Genes in Chinese Flowering Cabbage

Abstract

Plant-specific WRKY transcription factors (TFs) have been implicated to function as regulators of leaf senescence, but their association with postharvest leaf senescence of economically important leafy vegetables, is poorly understood. In this work, the characterization of a Group IIe WRKY TF, BrWRKY65, from Chinese flowering cabbage (Brassica rapa var. parachinensis) is reported. The expression of BrWRKY65 was up-regulated following leaf chlorophyll degradation and yellowing during postharvest senescence. Subcellular localization and transcriptional activation assays showed that BrWRKY65 was localized in the nucleus and exhibited trans-activation ability. Further electrophoretic mobility shift assay (EMSA) and transient expression analysis clearly revealed that BrWRKY65 directly bound to the W-box motifs in the promoters of three senescence-associated genes (SAGs) such as BrNYC1 and BrSGR1 associated with chlorophyll degradation, and BrDIN1, and subsequently activated their expressions. These findings demonstrate that BrWRKY65 may be positively associated with postharvest leaf senescence, at least partially, by the direct activation of SAGs. Taken together, these findings provide new insights into the transcriptional regulatory mechanism of postharvest leaf senescence in Chinese flowering cabbage.

Characterization of a Transcriptional Regulator, BrWRKY6, Associated with Gibberellin-Suppressed Leaf Senescence of Chinese Flowering Cabbage

“…35 Relative electrolytic leakage was determined as previously described. 3 RNA Extraction, cDNA Synthesis, Gene Cloning and Sequence Analysis. Total RNA of sampled tissues was isolated by use of an RNeasy plant mini kit (Qiagen) according to the manufacturer's instructions.…”

“…In our previous study, we also found that BrWRKY65 from Chinese flowering cabbage may be acting as a positive regulator of leaf senescence by activating three senescence-associated genes (SAGs). 3 Moreover, WRKY TFs are demonstrated to be involved in various physiological processes controlled by GA. 30 For instance, three WRKY TFs of rice, including OsWRKY24, -53, and -70, negatively regulate GA signaling in aleurone cells. 31 WRKY12 and WRKY13 mediate the GA 3 -controlled flowering time in Arabidopsis.…”

Identification of conserved and novel miRNAs responsive to heat stress in flowering Chinese cabbage using high-throughput sequencing

“…It often suffers from high-temperature stress in summer 6 , which not only influences plant growth and performance but results in yield reductions and even death 7 . Flowering Chinese cabbage genotypes can have obvious premature leaf senility, fine flowering stalks, significantly reduced photosynthetic capacity, and high electrolytic leakage and malondialdehyde content under high-temperature condition 8,9 .…”

The Cotton GhWRKY91 Transcription Factor Mediates Leaf Senescence and Responses to Drought Stress in Transgenic Arabidopsis thaliana

“…WRKY TFs can be divided into three groups [I, II (IIa-e), and III] on the basis of their structure and evolutionary history (Eulgem et al, 2000; Rushton et al, 2010). WRKY TFs can interact with W-box cis-elements [TTGAC(C/T)] in the promoter regions of downstream genes to regulate the expression of those genes, thus leading to improved plant adaptation to environmental changes (Fan et al, 2017).…”

“…In rice, OsWRKY23 has been shown to be involved in dark-induced leaf senescence in transgenic Arabidopsis plants (Jing et al, 2009). WRKY TFs are also involved in vegetative and fruit senescence, including BrWRKY65 in Chinese flowering cabbage (Fan et al, 2017) and LcWRKY1 in litchi (Jiang et al, 2017). Two cotton WRKY TFs, GhWRKY27 (Gu et al, 2019) and GhWRKY42 (Gu et al, 2018b), were recently identified to promote leaf senescence in transgenic Arabidopsis plants, suggesting that WRKY TFs have important roles during leaf senescence in cotton.…”