‘Candidatus Phytoplasma solani’ Predicted Effector SAP11-like Alters Morphology of Transformed Arabidopsis Plants and Interacts with AtTCP2 and AtTCP4 Plant Transcription Factors

Phytoplasmas are obligate intracellular pathogens that profoundly modify the development, physiology and behavior of their hosts by secreting effector proteins that disturb signal pathways and interactions both in plant and insect hosts. The characterization of effectors and their host-cell targets was performed for only a few phytoplasma species where it was shown that the SAP11 effector alters plant morphology by destabilizing plant transcription factors: TEOSINTE BRANCHED 1-CYCLOIDEA-PROLIFERATING CELL FACTOR (TCPs). To explore the possible role of the SAP11-like effector from '<i>Ca.</i> P. solani', we used <i>Arabidopsis thaliana</i> as a model plant. The <i>SAP11-like</i> effector gene from '<i>Ca.</i> P. solani' was introduced into arabidopsis by floral dip and transgenic lines were regenerated. <i>In planta</i> bimolecular fluorescence complementation (BIFC) assays in agroinfiltrated <i>Nicotiana benthamiana</i> leaf cells were conducted to detect interactions between SAP11-like and AtTCP2 and AtTCP4 using confocal microscopy. SAP11-like from '<i>Ca.</i> P. solani' induced significant phenotypic changes in arabidopsis, including crinkled leaves with reduced size, lower biomass, more axillary branches, changes in root morphology, and crinkled and smaller siliques. The BIFC assays proved <i>in planta</i> interaction of SAP11-like effector with AtTCP2 and AtTCP4. To our knowledge, this is the first characterization of the interaction between the '<i>Ca.</i> P. solani' effector and plant transcription factors, suggesting a potential mechanism of modulating plant development and induction of characteristic symptoms in '<i>Ca.</i> P. solani'-infected plants.