Related to ABI3 and VP1 (RAV) transcription factors belong to the AP2 and B3 superfamily.  RAVs genes have been reported to be involved in plant growth and development regulation.  This study screened three RAV genes from Medicago truncatula and named one of them MtRAV1.  The MtRAV1 overexpressing plants exhibits traits such as plant dwarfing, delayed flowering, reduced leaf and floral organs, increased branching, and reduced pods and seeds.  Gene expression analysis results showed that overexpression of MtRAV1 inhibited the expression of Flowering Locus T (MtFTa1), Suppressor of Overexpression of CO 1 (MtSOC1), GA3-oxidase1 (MtGA3OX1), DWARF14 (MtD14) and Carotenoid Cleavage Dioxygenase 7 (MtCCD7).  To further investigate the regulation pathway involved by MtRAV1, RNA-sequencing (RNA-seq) and DNA affinity purification sequencing (DAP-seq) analysis were conducted.  RNA-seq results indicated that MtRAV1 might affect plant growth and development by regulating some genes in photosynthesis, circadian rhythm and plant hormone signaling pathways, especially the auxin signaling pathway.  Conjoint analysis of DAP-seq and RNA-seq revealed that MtRAV1 might inhibit the expression of Ferredoxin (MtFd-l3), Light-harvesting Chlorophyll a/b Binding Protein 1 (MtLhcb-l2) and Small Auxin Up-regulated RNA (MtSAUR-l), which related to photosystem II and auxin signaling pathway.  Summarily, MtRAV1 was preliminarily proven to be a key growth inhibitory factor in M. truncatula.

The two-spotted spider mite, Tetranychus urticae Koch, is one of the most harmful pests in many agroecosystems worldwide.  To effectively manage this pest, there is an urgent need to develop novel bio-active acaricides that support integrated pest management strategies targeting T. urticae.  In this study, we explored the acaricidal effects of xenocoumacin 1 (Xcn1) on T. urticae and its predator Neoseiulus californicus using the highly purified compound.  Xcn1 was extracted and purified from the cell-free supernatant of the Xenorhabdus nematophila CB6 mutant constructed by the easy promoter activated compound identification (easyPACId) method.  When the concentration of Xcn1 exceeded 100 μg mL^–1, the survival rate of spider mite adults declined to below 40% and the fecundity was decreased by 80% at six days post-application.  At concentrations of 25 and 50 μg mL^–1, Xcn1 significantly impeded spider mite development by inhibiting the molt.  However, neither concentration had any adverse effects on the survival or reproduction of the predatory mite N. californicus.  The results from laboratory and semi-field experiments consistently demonstrated the effectiveness of the antimicrobial metabolite Xcn1 in controlling pest mites at both the molecular and physiological levels.  Our study offers a promising possibility that combines the compatible biocontrol agents of Xcn1 and predatory mites for integrated pest mite control.

Vegetable fields are often contaminated by heavy metals, and Spodoptera exigua is a major vegetable pest which is stressed by heavy metals mainly by feeding.  In this study, cadmium accumulation in the tissues of S. exigua exposed to cadmium and its effects on the growth and development of the parents and the offspring were investigated.  Under the stress of different concentrations of cadmium (0.2, 3.2, and 51.2 mg kg^–1), the cadmium content in each tissue of S. exigua increased in a dose-dependent manner.  At the larval stage, the highest cadmium accumulation was found in midgut in all three cadmium treatments, but at the adult stage, the highest cadmium content was found in fat body.  In addition, the cadmium content in ovaries was much higher than in testes.  When F₁ S. exigua was stressed by cadmium and the F₂ generation was not fed a cadmium-containing diet, the larval survival, pupation rate, emergence rate and fecundity of the F₂ generation were significantly reduced in the 51.2 mg kg^–1 treatment compared to the corresponding F₁ generation.  Even in the F₂ generation of the 3.2 mg kg^–1 treatment, the fecundity was significantly lower than in the parental generation.  The fecundity of the only-female stressed treatment was significantly lower than that of the only-male stressed treatment at the 3.2 and 51.2 mg kg^–1 cadmium exposure levels.  When only mothers were stressed at the larval stage, the fecundity of the F₂ generation was significantly lower than that of the F₁ generation in the 51.2 mg kg^–1 treatment, and it was also significantly lower than in the 3.2 and 0.2 mg kg^–1 treatments.  The results of our study can provide useful information for forecasting the population increase trends under different heavy metal stress conditions and for the reliable environmental risk assessment of heavy metal pollution.