Flavonols and flavanones are important bioactive compounds with multiple pharmacological activities and health benefits. Transcriptional activation of flavonol and flavanone biosynthesis has been studied extensively, while little is known about the negative regulators. CRISPR/Cas9 gene-editing technology, with the advantage of precise genetic modification, is a desirable tool for breeding biofortified materials and exploring potential molecular mechanisms. In this study, a transcriptional repressor, SlMYB32, was characterized in tomato fruit. Phenotype and metabolomic analyses confirmed that knockout of SlMYB32 resulted in increased accumulation of flavonols and flavanones, especially about 1 mg g–1 FW of quercetin 3-O-rutinoside (rutin). Transcriptome analysis indicated that expression of key genes SlPAL6, Sl4CL3 and Sl4CL4 as well as five candidate SlUGTs were significantly up-regulated in slmyb32 mutants. Dual-luciferase and EMSA assays indicated SlMYB32 could bind to and repress promoter activities of SlPAL6 and Sl4CL3. Expression of 27 transcription factors belonging to 12 families was significantly changed in slmyb32 mutants, among which two SlMYBs, two SlNACs, two SlAP2s and one SlWRKY were clustered with known flavonoid regulators. Our results provide new insights into improving bioactive compounds in fruit and understanding negative regulatory mechanisms in flavonol and flavanone biosynthesis.
Quinoa–peanut relay intercropping is a potential practice in saline-alkali land; however, quinoa varieties exhibit considerable variability, and a paucity of information regarding suitable varieties of quinoa for intercropping with peanuts. A field experiment with three intercropped peanut treatments (PSE, PMM, and PTL) with quinoa varieties of short-stemmed and early-maturing (QSE), medium-stemmed and medium-maturing (QMM), and tall-stemmed and late-maturing (QTL) was conducted in 2021–2022 to elucidate the effects of quinoa varieties on the root distribution, soil moisture content (SMC), electrical conductivity (EC), nutrient (N, P, and K) absorption, and pod yield of peanuts. The results showed the pod yield, pod dry weight, biomass, and 100-fruit weight of peanut under PSE were the highest, followed by PMM, and PTL was the lowest. The pod yield of PSE was 6.03–21.16% higher than that of PMM and PTL in 2021 and 2022. In the co-growth period of quinoa and peanut (CGP), the main stem height, branch number, leaf area (LA), dry matter weight, and nutrients absorption of peanut plants under PSE and PMM were all significantly higher than PTL; but no difference was observed between PSE and PMM. In the solo-growth period of peanut (SGP), the plant traits (except for the main stem height) and nutrient absorption of peanut under PMM were worse than PSE, and PTL was the worst, which was consistent with the variation of root length density (RLD) of peanuts. Meanwhile, PSE had the highest SMC at soil depths below 10 cm, nutrient contents in rhizosphere soil (K+, NO3−, NH4+, PO43−, and TOC), also EC and Na+ contents compared with PMM and PTL. The RLD of peanut, SMC, EC, and nutrient contents in rhizosphere soil of peanuts were negatively correlated with the RLD of quinoa. Therefore, intercropping peanut with short-stemmed and early-maturing quinoa variety is more conducive to increasing peanut yield in saline-alkali soil.