Induction of ethylene biosynthesis by aphids increases the susceptibility of several plant species to aphids. Recent studies have indicated that some MYB transcription factors regulate the phloem-based defense against aphid infestation by modulating ethylene (ET) signaling. Arabidopsis MYB102 has previously been shown to be induced by wound signaling and regulate defense response against chewing insects. However, it remains unclear whether Arabidopsis MYB102 takes part in the defense response of plants to aphids. Here, we investigated the function of MYB102 in the response of Arabidopsis to aphid infestation. Arabidopsis MYB102 was primarily expressed in vascular tissues, and its transcription was remarkably induced by green peach aphids (GPA; Myzus persicae). The results of RNA-Sequencing revealed that overexpression of MYB102 in Arabidopsis promoted ET biosynthesis by upregulation of some 1-aminocyclopropane-1-carboxylate synthase (ACS) genes, which are rate-limiting enzymes of the ET-synthetic pathway. Enhanced ET levels led to reduced Arabidopsis resistance to GPA. Furthermore, dominant suppression of MYB102 inhibited aphid-induced increase of ET levels in Arabidopsis. In agreement with a negative regulatory role for ET in aphid defense responses, the MYB102-overexpressing lines were more susceptible to GPA than wild-type (WT) plants. Overexpression of MYB102 in Arabidopsis obviously repressed aphid-induced callose deposition. Conversely, overexpression of MYB102 failed to increase aphid susceptibility in both the ET-insensitive mutants and plants treated with inhibitors of ET signaling pathways, demonstrating that the ET was critical for promoting aphid performance conferred by overexpression of MYB102. Collectively, our findings indicate that the Arabidopsis MYB102 increases host susceptibility to GPA through the ET-dependent signaling pathways.

Pogostemon auricularius, an aromatic plant in Lamiaceae, has wide application in pharmaceutical preparations. However, little is known about the secretory structures that contain the medicinal compounds. In this study, two kinds of glandular trichome types, including peltate glandular trichomes and short-stalked capitate trichomes, were identified in the leaves and stems by cryo-scanning electron microscope. Oil secretion from the glands contained lipids, flavones, and terpenes, and the progresses of secretion were different in the two glands types. The investigation by transmission electron microscope indicated that the endoplasmic reticulum system and plastids were involved in the biosynthesis of oils in the two glandular trichomes. The vacuoles showed a new role in the oil preparations and storage. The synthesized oil could be transported from the head cell to the sub-cuticular space by different way in the two glands. Comparative analysis of the development, distribution, histochemistry and ultrastructures of the secretory structures in Pogostemon auricularius led us to propose that the two glands may make different contribution to the collection of medicinal compounds. Furthermore, the characteristics of two glands in the secretory stage probably indicated the synthesizing site of metabolite.

In this research, our objective was to investigate the combined impact of microbial extracts and chemical fungicides on Northern corn leaf blight (NCLB), which is induced by Exserohilum turcicum, and the growth-promoting effect of the crude extracts was also determined. NCLB poses a serious threat to global maize production, necessitating sustainable and environmentally friendly solutions. Mycelial growth rate assays were used to assess the single or synergistic effects of microbial crude extracts and chemical fungicides, and the seed-soaking and root irrigation method was used to detect the growth-promoting effect of the crude extracts on maize seedlings. The results revealed an 84.60% inhibition rate of B. amyloliquefaciens gfj-4 against E. turcicum, and with an EC₅₀ of 49.01 mg·L⁻¹ for the crude extracts. Chemical fungicides demonstrated varying toxicity levels, with fludioxonil exhibiting the highest potency. The mixture of the crude extracts and pyraclostrobin at an 8:2 volume ratio displayed the highest toxicity ratio of 1.24, indicating a synergistic effect. The selected combinations exhibited strong synergistic effects. Soaking maize seeds with 80 mg·L⁻¹ of the crude extracts followed by root irrigation with 40 mg·L⁻¹ produced the most significant growth-promoting effect on maize seedlings. This study highlights the potential of microbial crude extracts to enhance the control of NCLB when combined with pyraclostrobin, along with its growth-promoting effects on maize seedlings.

Soil microbial community changes imposed by the cumulative effects of root-secreted phenolic acids (PAs) promote soil-borne pathogen establishment and invasion under monoculture systems, but the disease-suppressive soil often exhibits less soil-borne pathogens compared with the conducive soil. So far, it remains poorly understood whether soil disease suppressiveness is associated with the alleviated negative effects of PAs, involving microbial degradation. Here, the long-term monoculture particularly shaped the rhizosphere microbial community, for example by the enrichment of beneficial Pseudomonas species in the suppressive soil and thus enhanced disease-suppressive capacity, however this was not observed for the conducive soil. In vitro PA-degradation assays revealed that the antagonistic Pseudomonas species, together with the Xanthomonas and Rhizobium species, significantly increased the efficiency of PA degradation compared to single species, at least partially explaining how the suppressive soil accumulated lower PA levels than the conducive soil. Pot experiments further showed that this consortium harboring the antagonistic Pseudomonas species can not only lower PA accumulation in the 15-year conducive soils, but also confer stronger Fusarium wilt disease suppression compared with a single inoculum with the antagonistic bacteria. Our findings demonstrated that understanding microbial community functions, beyond the single direct antagonism, facilitated the construction of active consortia for preventing soil-borne pathogens under intensive monoculture.

Beneficial rhizobacteria can inhibit foliar pathogen infection by activation of defense responses, yet it the mechanisms of rhizobacteria-induced disease resistance remain largely unknown. Here, inoculation of susceptible maize plants with Pseudomonas fluorescens MZ05 significantly reduced disease occurrence caused by the leaf pathogen Setosphaeria turcica. Gene expression profiles of MZ05-inoculated plants were investigated by RNA-sequencing analyses, showing that several differentially expressed genes were positively associated with the metabolic processes of benzoxazinoids. Accordantly, the inoculation with P. fluorescens MZ05 resulted in a significant increase in the levels of 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) in the maize leaves. Furthermore, pre-inoculation with P. fluorescens MZ05 enhanced the transcription of two defense-related marked genes PAL and PR2a, as well as BX2 and GLU2, which are involved in DIMBOA biosynthesis, in pathogen-infected leaves. Defense responses in the inoculated plants were also greatly stronger and quicker than that in non-inoculated plants after pathogen attacks. However, virus-mediated silencing of BX2 or GLU2 remarkably attenuated the MZ05-induced effects, as evidenced by more disease occurrence and lower transcription of PAL and PR2a. Collectively, these findings indicated that the MZ05-induced increases of DIMBOA levels participated in the mediation of priming, which was the key mechanism in the rhizobacteria-induced host resistance.