The transcription factor MYB1 activates DGAT2 transcription to promote triacylglycerol accumulation in sacha inchi (Plukenetia volubilis L.) leaves under heat stress.

Triacylglycerol (TAG) accumulation is frequently triggered in vegetative tissues experiencing heat stress, which may increases plant basal plant thermo-tolerance by sequestering the toxic lipid intermediates that contribute to membrane damage or cell death under stress conditions. However, stress-responsive TAG biosynthesis and the underlying regulatory mechanisms are not fully understood. Here, we investigated the lipidomic and transcriptomic landscape under heat stress in the leaves of sacha inchi (Plukenetia volubilis L.), an important oilseed crop in tropical regions. Under heat stress (45 °C), the content of polyunsaturated TAGs (e.g., TAG18:2 and TAG18:3) and total TAGs were significantly higher, while those of unsaturated sterol esters, including ZyE 28:4, SiE 18:2 and SiE 18:3, were dramatically lower. Transcriptome analysis showed that the expression of PvDGAT2-2, encoding a type II diacylglycerol acyltransferase (DGAT) that is critical for TAG biosynthesis, was substantially induced under heat stress. We confirmed the function of PvDGAT2-2 in TAG production by complementing a yeast mutant defective in TAG biosynthesis. Importantly, we also identified the heat-induced transcription factor PvMYB1 as an upstream activator of PvDGAT2-2 transcription. Our findings on the molecular mechanism leading to TAG biosynthesis in leaves exposed to heat stress have implications for improving the biotechnological production of TAGs in vegetative tissues, offering an alternative to seeds.

Haplotype-resolved chromosomal-level genome assembly of Buzhaye (Microcos paniculata).

Microcos paniculata is a shrub used traditionally as folk medicine and to make herbal teas. Previous research into this species has mainly focused on its chemical composition and medicinal value. However, the lack of a reference genome limits the study of the molecular mechanisms of active compounds in this species. Here, we assembled a haplotype-resolved chromosome-level genome of M. paniculata based on PacBio HiFi and Hi-C data. The assembly contains two haploid genomes with sizes 399.43 Mb and 393.10 Mb, with contig N50 lengths of 43.44 Mb and 30.17 Mb, respectively. About 99.93% of the assembled sequences could be anchored to 18 pseudo-chromosomes. Additionally, a total of 482 Mb repeat sequences were identified, accounting for 60.76% of the genome. A total of 49,439 protein-coding genes were identified, of which 48,979 (99%) were functionally annotated. This haplotype-resolved chromosome-level assembly and annotation of M. paniculata will serve as a valuable resource for investigating the biosynthesis and genetic basis of active compounds in this species, as well as advancing evolutionary phylogenomic studies in Malvales.

Simultaneous determination of four alkaloids in Solanum lyratum Thunb by UPLC-MS/MS method.

Four alkaloids, strychnine, soladulcidine, solamargine and (3-O-beta-D-glucopyranosyl-(1 --> 2)beta-D-glucopyranosyl-(1 --> 4)-beta-D-galactopyranoside-(25xi)-solanidan-3beta,23beta-diol)(abbreviation, glycoalkaloid A) were isolated from Solanum lyratum Thunb. The structures were elucidated by NMR and measuring physicochemical properties. Then a novel and rapid method using an ultra-performance liquid chromatography coupled with mass spectrometry was developed and validated for the simultaneous determination of these compounds. An acquit UPLC BEH C18 column (2.1 mm x 50 mm, 1.7 microm) was used. Acetonitrile and 0.1% formic acid were adopted as mobile phase. Detection was performed on a Waters Micromass Quattro Premier tandem quadrupole mass spectrometer in the positive ion mode using an electrospray source. The multiple reaction monitoring (MRM) mode was used to detect the target compounds. The established method showed a good linearity (R2 > 0.999 0) over the investigated concentration ranges, good inter-day and intra-day precisions (less than 2%) and good recoveries (from 99.8% to 100.1%) for all four target compounds. Compared to previous methods employing conventional high performance liquid chromatography (HPLC) separation, the ultra-high-pressure liquid chromatography-tandem mass spectrometry achieved preferable chromatographic parameters and significantly increased sample throughput.