Disease resistance conferred by components of essential chrysanthemum oil and the epigenetic regulation of OsTPS1

The sesquiterpene alpha-bisabolol is the predominant active ingredient in essential oils that are highly valued in the cosmetics industry due to its wound healing,anti-inflammatory,and skin-soothing properties.Alpha-bisabolol was thought to be restricted to Compositae plants.Here we reveal that alpha-bisabolol is also synthesized in rice,a non-Compositae plant,where it acts as a novel sesquiterpene phytoalexin.Overexpressing the gene responsible for the biosynthesis of alpha-bisabolol,Os TPS1,conferred bacterial blight resistance in rice.Phylogenomic analyses revealed that alpha-bisabolol-synthesizing enzymes in rice and Compositae evolved independently.Further experiments demonstrated that the natural variation in the disease resistance level was associated with differential transcription of Os TPS1 due to polymorphisms in its promoter.We demonstrated that Os TPS1 was regulated at the epigenetic level by JMJ705 through the methyl jasmonate pathway.These data reveal the cross-family accumulation and regulatory mechanisms of alpha-bisabolol production.

Watermelon domestication was shaped by stepwise selection and regulation of the metabolome

Although crop domestication has greatly aided human civilization,the sequential domestication and regulation of most quality traits remain poorly understood.Here,we report the stepwise selection and regulation of major fruit quality traits that occurred during watermelon evolution.The levels of fruit cucurbitacins and flavonoids were negatively selected during speciation,whereas sugar and carotenoid contents were positively selected during domestication.Interestingly,fruit malic acid and citric acid showed the opposite selection trends during the improvement.We identified a novel gene cluster(CGC1,cucurbitacin gene cluster on chromosome 1)containing both regulatory and structural genes involved in cucurbitacin biosynthesis,which revealed a cascade of transcriptional regulation operating mechanisms.In the CGC1,an allele caused a single nucleotide change in Cl ERF1 binding sites(GCC-box)in the promoter of Cl Bh1,which resulted in reduced expression of Cl Bh1 and inhibition of cucurbitacin synthesis in cultivated watermelon.Functional analysis revealed that a rare insertion of 244 amino acids,which arose in C.amarus and became fixed in sweet watermelon,in Cl OSC(oxidosqualene cyclase)was critical for the negative selection of cucurbitacins during watermelon evolution.This research provides an important resource for metabolomics-assisted breeding in watermelon and for exploring metabolic pathway regulation mechanisms.

一个稻属特异存在的芳香族酚胺基因簇助力水稻广谱抗性

代谢基因簇(Biosynthetic Gene Cluster)由多个来源于不同酶家族的基因在染色体上相邻或是相近的位置组成.近十年来的研究发现,许多参与植物防御和具有重要医药价值的植物次生代谢物由植物代谢基因簇编码合成,但对此类基因簇的形成过程、生理功能以及进化等方面知之甚少.本研究综合利用基于代谢物的全基因组关联分析(m GWAS)、体外酶活力测定、植物稳定转化和烟草瞬时表达等多种手段在水稻10号染色体上发现并鉴定了一个芳香族酚胺基因簇——羟基肉桂酰酪胺(HT)基因簇.该基因簇由1个吡哆醇5′-磷酸氧化酶、1个酪氨酸脱羧酶和2个酰基转移酶组成,其终产物羟基肉桂酰酪胺具有植物抗毒素效应,能够显著提高水稻对两大典型病害(白叶枯和稻瘟病)的抗性.比较基因组学证据显示转座子(TEs)在HT基因簇关键组分的组装中发挥重要作用,侧面印证该基因簇的形成兼具"解毒"和"抗病"双重功效.进一步的进化分析表明, HT基因簇在稻属AA基因组分支中特异存在,其关键组分在这些植物中存在基因拷贝数和相对位置的变异.综上,本研究揭示了水稻芳香族酚胺基因簇的生化基础及其在水稻广谱抗性方面的作用,不仅为作物抗性方面的遗传改良提供了新资源,也为植物中代谢基因簇的形成机制和进化模式等方面提供了新的见解.