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Melatonin improves plant resistance to multiple stresses by participating in the biosynthesis of metabolites. Flavonoids are an important family of plant secondary metabolites and are widely recognized to be involved in resistance; however, the crosstalk between melatonin and flavonoid is largely unknown. We found that the resistance of pigeon pea (Cajanus cajan) to salt, drought, and heat stresses were significantly enhanced by pre-treatment with melatonin. Combined transcriptome and LC-ESI-MS/MS metabolomics analyses showed that melatonin significantly induced the enrichment of flavonoids and mediated the reprogramming of biosynthetic pathway genes. The highest fold-increase in expression in response to melatonin treatment was observed for the CcF3´H family, which encodes an enzyme that catalyses the biosynthesis of luteolin, and the transcription factor CcPCL1 directly bonded to the CcF3´H-5 promoter to enhance its expression. In addition, salt stress also induced the expression of CcPCL1 and CcF3´H-5 , and their overexpression in transgenic plants greatly enhanced salt tolerance by promoting the biosynthesis of luteolin. Overall, our results indicated that pre-treatment of pigeon pea with melatonin promoted luteolin biosynthesis through the CcPCL1 and CcF3´H-5 pathways, resulting in salt tolerance. Our study shows that melatonin enhances plant tolerance to multiple stresses by mediating flavonoid biosynthesis, providing new avenues for studying the crosstalk between melatonin and flavonoids. [ABSTRACT FROM AUTHOR]

The present study was designed to evaluate the chemical extraction, chemical composition, and antioxidant and antibacterial properties of the total flavonoids in Willow Buds (TFW). We investigated the optimal extraction of TFW using response surface methodology (RSM). Chemical compounds were analyzed using Q-Orbitrap LC–MS/MS. The DPPH radical scavenging capacity, hydroxy radical inhibitory ability, and superoxide anion radical inhibitory ability were explored to determine the antioxidant properties of flavonoid extractions. The antibacterial effect was assessed via minimal inhibitory concentration. The results demonstrated that the optimal extraction conditions were an ethanol concentration of 50%, a time of 35 min, and a liquid/material ratio of 70:1 mL/g. Under these conditions, the yield of TFW was 7.57%. Eight flavonoids, a phenolic glycoside, and an alkaloid were enriched in the Willow Buds. The TFW exhibited significant antioxidant activity, with IC50 values of 0.18-0.24 mg/mL and antimicrobial activity against Escherichia coli, Salmonella enterica, Staphylococcus aureus, and Streptococcus pneumoniae. TFW may be explored as potential and natural compounds in food and pharmacological applications. [ABSTRACT FROM AUTHOR]

SUMMARY: Calcineurin B‐like (CBL)‐interacting protein kinases (CIPKs) play a central role in Ca2+ signalling and promote drought tolerance in plants. The CIPK gene family in pigeon pea (Cajanus cajan L.), a major food crop affected by drought, has not previously been characterised. Here, we identified 28 CIPK genes in the pigeon pea genome. Five CcCIPK genes were strongly upregulated in roots upon drought treatment and were selected for further characterisation. Overexpression of CcCIPK13 and CcCIPK14 increased survival rates by two‐ to three‐fold relative to controls after 14 days of drought. Furthermore, the three major flavonoids, genistin, genistein and apigenin, were significantly upregulated in the same transgenic plants. Using CcCIPK14 as bait, we performed a yeast two‐hybrid screen and identified six interactors, including CcCBL1. CcCIPK14 exhibited autophosphorylation and phosphorylation of CcCBL1 in vitro. CcCBL1‐overexpressed plants displayed higher survival rates upon drought stress as well as higher expression of flavonoid biosynthetic genes and flavonoid content. CcCIPK14‐overexpressed plants in which CcCBL1 transcript levels were reduced by RNA interference had lower survival rates, which indicated CcCBL1 in the same pathway as CcCIPK14. Together, our results demonstrate a role for the CcCIPK14‐CcCBL1 complex in drought stress tolerance through the regulation of flavonoid biosynthesis in pigeon pea. Significance Statement: This study systematically elucidates the mechanism by which the CIPK‐CBL complex regulates flavonoid accumulation and drought resistance in pigeon pea, which lays a foundation for in‐depth exploration of relevant molecular mechanisms in plants. [ABSTRACT FROM AUTHOR]

A novel approach for synchronous extraction and enrichment of hydrophilic component and hydrophobic component with CO 2 -based switchable-solvent (SHS) from pigeon pea leaves was developed in the present study. After screening of SHS, N, N-dimethyl-cyclohexylamine (DMCHA)/water system was selected as the properest SHS for the extraction and enrichment process. To optimize this process, we conducted single factor experiments with the Box-Behnken design. The optimal parameters were as follows: solid-liquid ratio R (S/L) 40:1 (mg/mL), ultrasound time 15 min and bubbling CO 2 time 79 min (0.5 mL/s). Under the circumstances, the extraction yields of representative flavonoid vitexin and stilbene cajaninstilbenes acid (CSA) reached 1.80 ± 0.12 mg/g and 9.32 ± 0.08 mg/g, respectively, which were 1.06 and 1.49 folds to those by the traditional methods. And the contents of target compounds vitexin and CSA in the enriched extracts were 2.3% and 12.1%, which increased above 6.76 and 4.58 folds to that in extracts using 65% ethanol-UAE. And the results suggested that the N, N-dimethyl-cyclohexylamine (DMCHA)/water system can be guaranteed for at least 5 cycles with relatively stable extraction yields of vitexin and CSA. Furthermore, a theoretical study using density functional theory was put into effect to explore the properties of SHS and their relationship with the vitexin and CSA. The mechanism study showed that SHS had higher biocompatibility with target compounds due to the H-bonds. The present method was an eco-friendly, promising, and sustainable alternative to extract and enrich simultaneously hydrophilic and hydrophobic phytochemicals from plant materials. Image 1 • This paper developed a novel approach for efficient and recyclable extraction and enrichment of phytochemicals from the disused pigeon pea leaves in one solvent system. • The mechanism study showed that SHS had higher biocompatibility with target compounds due to the H-bonds using the density functional theory. • The switchable solvents have usually been used in the extraction of oil. Moreover, the exploit of SHS considering bioactive compounds from plants material has hardly been reported yet. [ABSTRACT FROM AUTHOR]