Integrated transcriptome and metabolite profiling highlights the role of benzoxazinoids in wheat resistance against Fusarium crown rot

Fusarium crown rot(FCR), caused by Fusarium spp., is a chronic and severe plant disease worldwide. In the last years, the incidence and severity of FCR in China has increased to the point that it is now considered a threat to local wheat crops. In this study, for the first time, the metabolites and transcripts responsive to FCR infection in the partial resistant wheat cultivar 04 Zhong 36(04 z36) and susceptible cultivar Xinmai 26(XM) were investigated and compared at 20 and 25 days post inoculation(dpi). A total of 443 metabolites were detected, of which 102 were significantly changed because of pathogen colonization.Most of these 102 metabolites belonged to the flavonoid, phenolic acid, amino acid and derivative classes.Some metabolites, such as proline betaine, lauric acid, ribitol, and arabitol, were stably induced by Fusarium pseudograminearum(Fp) infection at two time points and may have important roles in FCR resistance. In line with the reduced seedling height of 04 z36 and XM plants, RNA-seq analysis revealed that FCR infection significantly affected the photosynthesis activities in two cultivars. Furthermore, 15 jasmonate ZIM-domain genes(JAZ) in the significantly enriched ‘regulation of jasmonic acid mediated signaling pathway’ in 04 z36 were down-regulated. The down-regulation of these JAZ genes in 04 z36 may cause a strong activation of the jasmonate signaling pathway. Based on combined data from gene expression and metabolite profiles, two metabolites, benzoxazolin-2-one(BOA) and 6-methoxy-benzoxazolin-2-one(MBOA), involved in the benzoxazinoid-biosynthesis pathway, were tested for their effects on FCR resistance. Both BOA and MBOA significantly reduced fungal growth in vitro and in vivo, and, thus, a higher content of BOA and MBOA in 04 z36 may contribute to FCR resistance. Above all, the current analysis extends our understanding of the molecular mechanisms of FCR resistance/susceptibility in wheat and will benefit further efforts for the genetic improvement of disease resistance.

Changes in concentrations and transcripts of plant hormones in wheat seedling roots in response to Fusarium crown rot

Fusarium crown rot(FCR) is a soilborne disease causing severe yield losses in many wheat-growing areas of the world. Diseased plants show browning and necrosis of roots and stems causing white heads at maturity. Little is known about the molecular processes employed by wheat roots to respond to the disease. We characterized morphological, transcriptional and hormonal changes in wheat seedling roots following challenge with Fusarium pseudograminearum(Fp), the main pathogen of FCR. The pathogen inhibited root development to various extents depending on plants' resistance level. Many genes responsive to FCR infection in wheat roots were enriched in plant hormone pathways. The contents of compounds involved in biosynthesis and metabolism of jasmonic acid, salicylic acid, cytokinin and auxin were drastically changed in roots at five days post-inoculation. Presoaking seeds in methyl jasmonate for 24 h promoted FCR resistance, whereas presoaking with cytokinin 6-benzylaminopurine made plants more susceptible. Overexpression of TaOPR3, a gene involved in jasmonic acid biosynthesis, enhanced plant resistance as well as root and shoot growth during infection.

Thermal stability of Te nanowires and their crystallographydetermined surface evolution at elevated temperatures

Nanowires are fantastic nanostructures for designing new functional devices because of their extraordinary properties.However,nanowires usually suffer pronounced size and surface effects with decreasing diameter size.Whether their structure and thermal stability can still fill the requirements of practical applications is a critical issue to be figured out.Herein,Te nanowires with diameters ranging from sub-10 to over 80 nm are used as samples to probe into this issue.In situ heating experiments are performed on these Te nanowires using an aberration-corrected transmission electron microscopy combined with a chip-based heating holder.It is found that Te nanowires suffer sublimation at elevated temperatures rather than melting,showing sizedependent sublimation scenarios.The Te nanowires with diameter smaller than 20 nm sublimate below 205℃,while the larger ones with diameter around 85 nm require a higher temperature of around 225℃.During sublimation-induced shape evolution,the interfacial wetting equilibrium and crystal orientations play critical roles,leading to the formation of spherical surfaces or featured facets at the free surfaces.A mean contact angle of 107.5°is determined at the C-Te interface when the crystalline Te nanowires stay in a quasi-liquid equilibrium state.However,once the crystalline feature is overwhelming,e.g.,at moderate temperatures,the(1011),(1120),and(1010)facets govern the free surface,despite the wetting condition at the interfaces.