Macro Plant Projection Imaging (MAPPI): An open, scalable platform for whole-plant fluorescence real-time imaging

The bid to understand long distance Ca²⁺ signaling patterns in co-ordinating whole-plant responses to systemic or induced defense have been scarce in soil-grown plants mainly due to limitations of conventional microscopy. Macro Plant Projection Imaging (MAPPI), a real-time, low-cost, dual-view fluorescence imaging platform was developed by Tortora and colleagues for whole plant visualization of mature soil grown plants.  The biggest advantage of MAPPI is its large field of view and compatibility with genetically encoded fluorescent indicators. The authors validated the  MAPPI system to monitor wound-induced long distance Ca²⁺ wave dynamics in Nicotiana benthamiana expressing GCaMP3 Ca²⁺ indicators (a genetically encoded, intensity based calcium indicator). Interestingly, different leaf stages exhibited distinct and varied GCaMP3 fluorescence responses but the platform was capable of detecting systemic Ca²⁺ waves from leaf to leaf during all stages of development. The same experimental design was also used to visualize apoplastic L-glutamate dynamics. Additionally, the authors monitored Ca²⁺ dynamics in plants subjected to submergence, and investigated if the long-distance Ca²⁺ waves also propagated from shoot-to-root, corroborating that long range Ca²⁺ waves are a conserved feature and not restricted to only model species. (Summary by Indrani Kakati @indranik333  @indranik18.bsky.social) Science Advances 10.1126/sciadv.aea4466