Strategic nanoparticle-mediated plant disease resistance.

Nanotechnology is a promising means for development of sustainable agriculture while the study of nanoparticle-mediated plant disease resistance is still in its primary stage. Nanotechnology has shown great promise in regulating: the content of secondary metabolites, inducing disease resistance genes, delivering hormones, delivering biomolecules (such as: nucleotides, proteins, and activators), and obtaining transgenic plants to resist plant diseases. In this review, we conclude its versatility and applicability in disease management strategies and diagnostics and as molecular tools. With the advent of new biotechnologies (e.g. de novo regeneration, CRISPR/Cas9, and GRF4-GIF1 fusion protein), we discuss the potential of nanoparticles as an optimal platform to deliver biomolecules to plants for genetic engineering. In order to ensure the safe use and social acceptance of plant nanoparticle technology, its adverse effects are discussed, including the risk of transferring nanoparticles through the food chain.

Jasmonate- and abscisic acid-activated AaGSW1-AaTCP15/AaORA transcriptional cascade promotes artemisinin biosynthesis in Artemisia annua.

Artemisinin, a sesquiterpene lactone widely used in malaria treatment, was discovered in the medicinal plant Artemisia annua. The biosynthesis of artemisinin is efficiently regulated by jasmonate (JA) and abscisic acid (ABA) via regulatory factors. However, the mechanisms linking JA and ABA signalling with artemisinin biosynthesis through an associated regulatory network of downstream transcription factors (TFs) remain enigmatic. Here we report AaTCP15, a JA and ABA dual-responsive teosinte branched1/cycloidea/proliferating (TCP) TF, which is essential for JA and ABA-induced artemisinin biosynthesis by directly binding to and activating the promoters of DBR2 and ALDH1, two genes encoding enzymes for artemisinin biosynthesis. Furthermore, AaORA, another positive regulator of artemisinin biosynthesis responds to JA and ABA, interacts with and enhances the transactivation activity of AaTCP15 and simultaneously activates AaTCP15 transcripts. Hence, they form an AaORA-AaTCP15 module to synergistically activate DBR2, a crucial gene for artemisinin biosynthesis. More importantly, AaTCP15 expression is activated by the multiple reported JA and ABA-responsive TFs that promote artemisinin biosynthesis. Among them, AaGSW1 acts at the nexus of JA and ABA signalling to activate the artemisinin biosynthetic pathway and directly binds to and activates the AaTCP15 promoter apart from the AaORA promoter, which further facilitates formation of the AaGSW1-AaTCP15/AaORA regulatory module to integrate JA and ABA-mediated artemisinin biosynthesis. Our results establish a multilayer regulatory network of the AaGSW1-AaTCP15/AaORA module to regulate artemisinin biosynthesis through JA and ABA signalling, and provide an interesting avenue for future research exploring the special transcriptional regulation module of TCP genes associated with specialized metabolites in plants.

AaCycTL Regulates Cuticle and Trichome Development in Arabidopsis and Artemisia annua L.

Artemisinin is an important drug for resistance against malaria. Artemisinin is derived from the glandular trichome of leaves, stems, or buds of the Chinese traditional herb Artemisia annua. Increasing the trichome density may enhance the artemisinin content of A. annua. It has been proven that cyclins are involved in the development of trichomes in tomato, Arabidopsis, and tobacco, but it is unclear whether the cyclins in A. annua influence trichome development. In this study, we showed that AaCycTL may regulate trichome development and affect the content of artemisinin. We cloned AaCycTL and found that it has the same expression files as the artemisinin biosynthesis pathway gene. We overexpressed AaCycTL in Arabidopsis, and the results indicated that AaCycTL changed the wax coverage on the surface of Arabidopsis leaves. The trichome density decreased as well. Using yeast two-hybrid and BiFC assays, we show that AaCycTL can interact with AaTAR1. Moreover, we overexpressed AaCycTL in A. annua and found that the expression of AaCycTL was increased to 82-195%. Changes in wax coverage on the surface of transgenic A. annua leaves or stems were found as well. We identified the expression of the artemisinin biosynthesis pathway genes ADS, CYP71AV1, and ALDH1 has decreased to 88-98%, 76-97%, and 82-97% in the AaCycTL-overexpressing A. annua lines, respectively. Furthermore, we found reduced the content of artemisinin. In agreement, overexpression of AaCycTL in A. annua or Arabidopsis may alter waxy loading, change the initiation of trichomes and downregulate trichome density. Altogether, AaCycTL mediates trichome development in A. annua and thus may serve to regulate trichome density and be used for artemisinin biosynthesis.