Down-regulation of acetolactate synthase compromises Ol-1- mediated resistance to powdery mildew in tomato

Abstract

BackgroundIn a cDNA-AFLP analysis comparing transcript levels between powdery mildew (Oidium neolycopersici)-susceptible tomato cultivar Moneymaker (MM) and near isogenic lines (NILs) carrying resistance gene Ol-1 or Ol-4, a transcript-derived fragment (TDF) M11E69-195 was found to be present in NIL-Ol-1 but absent in MM and NIL-Ol-4. This TDF shows homology to acetolactate synthase (ALS). ALS is a key enzyme in the biosynthesis of branched-chain amino acids valine, leucine and isoleucine, and it is also a target of commercial herbicides.ResultsThree ALS homologs ALS1, ALS2, ALS3 were identified in the tomato genome sequence. ALS1 and ALS2 show high similarity, whereas ALS3 is more divergent. Transient silencing of both ALS1 and ALS2 in NIL-Ol-1 by virus-induced gene silencing (VIGS) resulted in chlorotic leaf areas that showed increased susceptibility to O. neolycopersici (On). VIGS results were confirmed by stable transformation of NIL-Ol-1 using an RNAi construct targeting both ALS1 and ALS2. In contrast, silencing of the three ALS genes individually by RNAi constructs did not compromise the resistance of NIL-Ol-1. Application of the herbicide chlorsulfuron to NIL-Ol-1 mimicked the VIGS phenotype and caused loss of its resistance to On. Susceptible MM and On-resistant line NIL-Ol-4 carrying a nucleotide binding site and leucine rich repeat (NB-LRR) resistance gene were also treated with chlorsulfuron. Neither the susceptibility of MM nor the resistance of NIL-Ol-4 was affected.ConclusionsALS is neither involved in basal defense, nor in resistance conferred by NB-LRR type resistance genes. Instead, it is specifically involved in Ol-1-mediated resistance to tomato powdery mildew, suggesting that ALS-induced change in amino acid homeostasis is important for resistance conferred by Ol-1.

Knockdown of MLO genes reduces susceptibility to powdery mildew in grapevine

“…The formation of papillae is not the only process instigated by the activity of MLO genes. To understand the effect of MLO knockdown on other genes involved in plant–pathogen interaction, the expression of 13 genes known to be differentially expressed after PM inoculation 55–57 , 66 , 70–74 was analyzed. The knockdown of MLO genes in the TLB4 line did not affect the expression levels of the 13 considered genes as compared with the EVB line in absence of PM infection.…”

Agrobacterium-mediated transformation of tomato (Lycopersicon esculentumL. cv. Hezuo 908) with improved efficiency

“…function of genes [25] or gene products, by enhancing or inhibiting a specific gene expression in cells. [26] It also aids the production of recombinant siRNAs [9] or proteins [27] in cells, to ensure that the cells possess novel functions [28] or act as plant bioreactors. [29,30] The establishment of this protocol complements previous studies and improves tomato cultivar transformation.…”

Ethylene and Abscisic Acid Signaling Pathways Differentially Influence Tomato Resistance to Combined Powdery Mildew and Salt Stress

“…The reaction mix contained 5 μl 2× iQ SYBR GREEN super mix, 1 μl forward primer (3 μM), 1 μl reverse primer (3 μM), and 3 μl cDNA (or DNA, 20 ng) template, in a final volume of 10 μl. Thermocycling condition was 95°C for 3 min, followed by 40 cycles of 95°C for 30 s and 60°C for 30 s. Primers for tomato elongation factor 1α (EF) were Fw-EF-GGAACTTGAGAAGGAGCCTAAG and Rv-EF-CAACACCAACAGCAACAGTCT (Gao et al, 2014). The primers used to monitor the expression of tomato genes are described in Supplementary Table S1 .…”