Diseases caused by rust fungi pose a significant threat to global plant production. Although carotenoid pigments are produced in spores of nearly all rust species, the corresponding biosynthesis pathway(s) have not been investigated. Here, candidate genes for carotenoid biosynthesis in Puccinia graminis f. sp. tritici (Pgt) were identified, cloned and functionally complemented using specifically engineered strains of Escherichia coli. A part of the carotenoid biosynthesis pathway in rust fungi was elucidated, with only two genes, CrtYB and CrtI, catalysing the reactions from geranyl–geranyl diphosphate (GGPP) to γ-carotene. The CrtYB gene encodes a bi-functional lycopene cyclase/phytoene synthase, which catalyses the condensation of two GGPP into phytoene, as well as the cyclisation of the ψ-end of lycopene to form γ-carotene. The CrtI gene encodes a phytoene desaturase that carries out four successive desaturations of phytoene, through the intermediates phytofluene and neurosporene to lycopene. The evolution of carotenoid pigmentation in rust fungi, including Pgt, P. graminis avenae, P. graminis secalis (Pgs), P. graminis lolli, P. striiformis f. sp. tritici, P. striiformis f. sp. pseudohordei, P. striiformis f. sp. hordei, the “scabrum” rust (putative hybrids between Pgt and Pgs), P. triticina, and P. hordei, was investigated by phylogenetic analysis. Both CrtYB and CrtI were found to be closely related among rust fungi, other pathogenic fungi, and some aphids. Our results provide a springboard to increase the understanding of the physiological role(s) of carotenoid pigments in rust fungi, to better understand evolution within the Pucciniales, and to develop robust molecular diagnostics for rust fungi.

锈菌引起的疾病对全球植物生产构成重大威胁。尽管类胡萝卜素色素在几乎所有锈菌的孢子中产生，但尚未研究相应的生物合成途径。在这里，禾本科植物中类胡萝卜素生物合成的候选基因。SP 。使用专门设计的大肠杆菌菌株鉴定、克隆和功能性补充小麦(Pgt) 。阐明了锈菌中类胡萝卜素生物合成途径的一部分，只有两个基因，CrtYB和CrtI，催化香叶基-香叶基二磷酸 (GGPP) 到γ-胡萝卜素的反应。该CrtYB基因编码双功能番茄红素环化酶/八氢番茄红素合酶，催化两个GGPP缩合为八氢番茄红素，以及番茄红素ψ-末端环化形成γ-胡萝卜素。所述CRTI基因编码八氢番茄红素去饱和酶，其执行八氢番茄红素的四个连续去饱和，通过中间体六氢番茄红素和链孢番茄红素。锈菌类胡萝卜素色素沉着的演化，包括 Pgt、P. graminis avenae、P. graminis secalis (Pgs)、P. graminis lolli、P. striiformis f。SP 。小麦，条锈菌F。sp. pseudohordei，P. striiformis f. SP 。hordei、“scabrum”锈病（Pgt 和 Pgs 之间的假定杂交种）、P. triticina和P. hordei，通过系统发育分析进行了研究。无论CrtYB和CRTI发现锈菌，其它病原真菌，以及一些蚜虫之间密切相关。我们的研究结果提供了一个跳板，以增加对类胡萝卜素色素在锈菌中的生理作用的理解，更好地了解锈菌目内的进化，并为锈菌开发强大的分子诊断方法。