The plant growth-promoting effects of biostimulants have been widely documented, while little is known about the intrinsic mechanism. In our study, a pot experiment was conducted to investigate the effects of biostimulants on maize, and the maize root transcriptome and rhizosphere microbiome were assessed. The physicochemical properties of the soil were significantly altered with various trends, and the growth and yield of maize were promoted by biostimulants. Sampling time and maize strain were the strongest factors that altered the rhizosphere microorganisms. Rhizosphere microbiota with biostimulant application exhibited high community robustness. Root transcriptome analysis suggested an altered expression profile induced by biostimulants and maize strains. An integrated correlation analysis demonstrated that phosphate and nitrate metabolism genes are tightly associated with some rhizosphere microbiota. These results implied the plant growth-promoting effects of biostimulants might act in a rhizosphere microorganism-dependent manner and help to expand the use of biostimulants in sustainable agriculture.

Tetrastigma hemsleyanum Diels et Gilg is a rare and wild medicinal resource. Metabolites, especially secondary metabolites, have an important influence on T. hemsleyanum adaptability and its medicinal quality. The metabolite proanthocyanidin (PA) is a polyphenol compound widely distributed in land plants, which can be used as antioxidants and anticancer agents. Here, we discovered that three types of PA accumulated in large amounts in purple leaves (PL), but not in green leaves (RG), based on widely non-targeted metabolomics. In addition, we further found that catechins and their derivatives, which are the structural units of PA, are also enriched in PL. Afterwards, we screened and obtained five key genes, DNR1/2, ANS, ANR and LAR closely related to PA biosynthesis through transcriptome analysis and found they were all highly expressed in PL compared to RG. Therefore, observed the regulatory relationship between the main compounds and genes network, and the PA metabolism regulatory pathway was complicated, which may be different to other species.

Cadmium (Cd) is a strong toxic heavy metal pollutant, which poses a serious threat to plant development. Thus, it is vital important to understand the molecular mechanism of Cd accumulation, as to help reduce its potential toxicity to crops and maintain food security. MicroRNAs (miRNAs) act as critical gene regulators, participating in almost all abiotic stress processes. MiR535 is an ancient conserved miRNA, can be highly induced in the low concentration of Cd, but its biological functions in Cd stress is still unclear. In this study, we discovered that the OsSPL7 served as the main target gene of miR535. Moreover, rice overexpressing miR535 (OE535) promoted root length and Cd content, in contrast, plants knockout miR535 (mir535) and overexpressing OsSPL7 (SPL7myc) both had a reduced root length and Cd levels under Cd stress. Further, more Cd was translocated from rice husk to brown rice in OE535 plants but less translocated in mir535/SPL7OE plants. Most interesting and importantly, OsSPL7 could directly bind to the promoter of a major Cd transporter gene OsNramp5, and repress its transcripts levels to mediate Cd absorption. Collectively, this provides a new insight into the molecular basis of rice response to Cd stress by the miR535-SPL7-Nramp5 pathway.

Flowering time (or heading date in crops) is a critical agronomic trait for rice reproduction and adaptation. The circadian clock is an endogenous oscillator that is involved in controlling photoperiodic flowering. The rice LATE ELONGATED HYPOCOTYL (OsLHY), the core oscillator component of circadian clock, is a homolog of the LHY/CCA1 in Arabidopsis. Here we showed that CRISPR/Cas9-engineered mutations in OsLHY caused late flowering in rice only under long-day (LD) conditions. In the oslhy mutant, the diurnal expression of circadian clock-related genes was seriously affected under both LD and short-day (SD) conditions. Furthermore, the expression of the flowering activators Ehd1, Hd3a and RFT1 was down-regulated and flowering repressors Hd1 and Ghd7 was up-regulated in the oslhy mutant under LD conditions. While the transcripts of flowering-related genes were not dramatically influenced under SD conditions. Dual-luciferase assays showed that OsLHY repressed the transcription of OsGI, Hd1, Ghd7, Hd3a, RFT1 and OsELF3, and activated the transcription of Ehd1. Moreover, the yeast one hybrid assay confirmed that OsLHY directly repressed OsGI, RFT1 and OsELF3 by binding to their promoters, which is consistent with that in Arabidopsis. These results suggested that the OsLHY can promote rice flowering mainly through regulating Hd1 and Ehd1 under LD conditions.