Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín (EEZ) CSIC, Calle Profesor Albareda nº1, 18008, Granada, Spain.
Plant Molecular Biology Departments, Institute of Biotechnology, UNAM, Cuernavaca, Mor., Mexico.
J Plant Physiol. 2019 Jun;237:95-103. doi: 10.1016/j.jplph.2019.04.009. Epub 2019 Apr 24.
Arbuscular mycorrhizal (AM) formation enhances plant growth and fitness through improved uptake of water and mineral nutrients in exchange for carbon compounds to the AM fungus. The fungal structure for the reciprocal exchange of nutrients in the symbiosis is the arbuscule, and defence genes expressed in cells containing arbuscules could play a role in the control of hyphal spread and arbuscule formation in the root. We characterized and analyzed the Ptc52 gene from tomato (SlPtc52), a member of the gene family of non-heme oxygenases, whose function has been related to the lethal leaf spot 1 (Lls1) lesion mimic phenotype in plants which is sometimes associated with enhanced disease resistance. Sequence analysis of the SlPTC52 protein revealed conserved typical motifs from non-heme oxygenases, including a Rieske [2Fe-2S] motif, a mononuclear non-heme iron-binding motif and a C-terminal CxxC motif. The level of transcript accumulation was low in stem, flower and green fruits, and high in leaves. Although SlPtc52 expression was perceptible at low levels in roots, its expression increased concomitantly with AM fungus root colonization. Tomato non-mycorrhizal hairy roots expressing the GUS protein under the control of promoter SlPtc52 exhibited GUS activity in the endodermis, the apical meristem of the root tip and in the lateral root primordium. AM fungal colonization also resulted in intensive GUS activity that clearly corresponds to cortical cells containing arbuscules. SlPtc52 gene silencing led to a delay in root colonization and a decrease in arbuscular abundance, suggesting that SlPTC52 plays a regulatory role during AM symbiosis.
丛枝菌根（AM）的形成通过改善对水和矿物养分的吸收，同时将碳化合物交换给 AM 真菌，从而增强植物的生长和适应性。共生体中进行养分互惠交换的真菌结构是丛枝，并且在含有丛枝的细胞中表达的防御基因可能在控制菌丝体在根中的扩散和丛枝的形成中发挥作用。我们从番茄（SlPtc52）中鉴定和分析了 Ptc52 基因，该基因是非血红素加氧酶基因家族的成员，其功能与植物中的致死叶斑 1（Lls1）病变模拟表型有关，该表型有时与增强的抗病性有关。SlPTC52 蛋白的序列分析揭示了非血红素加氧酶的保守典型基序，包括 Rieske [2Fe-2S] 基序、单核非血红素铁结合基序和 C 末端 CxxC 基序。茎、花和绿果中的转录积累水平较低，而叶片中的转录积累水平较高。尽管 SlPtc52 在根中的表达水平较低，但在 AM 真菌根定殖时其表达水平会增加。在 SlPtc52 启动子控制下表达 GUS 蛋白的番茄非菌根毛状根在根内皮层、根尖的顶端分生组织和侧根原基中表现出 GUS 活性。AM 真菌的定殖也导致 GUS 活性增强，这与含有丛枝的皮层细胞明显对应。SlPtc52 基因沉默导致根定殖延迟和丛枝丰度减少，表明 SlPTC52 在 AM 共生中发挥调节作用。
