![]() ![]() Phytoplasmas form a monophyletic group that has common ancestry with Acholeplasma species ( Harrison et al. Within the Class Mollicutes, members of Ca. The majority of mollicutes live in close association with eukaryotic hosts as symbionts or pathogens and have undergone severe genome reductions. Phytoplasmas (genus ‘ Candidatus phytoplasma’) and other members of the Class Mollicutes are small bacteria with single cell membranes and no cell wall and are thought to have evolved from a Gram-positive Clostridium-like ancestor ( Bertaccini 2007 Hogenhout et al. These findings suggest that witches’ broom-affected parts of the trees contribute to WBDL epidemics by supporting higher phytoplasma titers and attracting insect vectors. Defense genes that have a role in plant defense responses to bacteria and insects are more downregulated in witches’ brooms compared with asymptomatic sections of trees. Moreover, the witches’ brooms were found to attract the vector leafhopper. Sampling of WBDLp-infected lime trees revealed that WBDLp titers and SAP11 WBDL expression levels were higher in symptomatic leaves compared with asymptomatic sections of the same trees. SAP11 WBDL interacts with acid lime ( Citrus aurantifolia) TCP transcription factors, specifically members of the TB1/CYC class that have a role in suppressing axillary branching in plants. Here we show that the gene encoding SAP11 of WBDLp ( SAP11 WBDL) is present in all WBDLp isolates collected from diseased trees. However, it is unclear how WBDL phytoplasma (WBDLp) induces witches’ broom symptoms and if these symptoms contribute to the spread of phytoplasma. ![]() An insect-transmitted phytoplasma causing Witches’ Broom Disease of Lime (WBDL) is responsible for the drastic decline in lime production in several countries. ![]()
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