Study On The Regulation Of Auxin Polar Transport To The Establishment Of The Proximal Axis Of Early Leaf Primordia

Leaf dorsiventrality – or most often called adaxial-abaxial leaf polarity – refers to the two opposing leaf faces which have different cell types performing distinct biological functions.In 1951,Ian Sussex reported that when an incipient leaf primordium was surgically isolated by an incision across the vegetative shoot apical meristem(SAM),a radialized structure without adaxial domain would form.This led to a proposal that a signal,now called the Sussex signal,is transported from SAM to emerging primordia to direct leaf adaxial-abaxial patterning.The plant hormone auxin has recently been proposed to be the Sussex signal,but whether this is the case was suggested to be further resolved.Through live imaging,we established a profile for auxin polar transport in and around young leaf primordia.We show that the auxin polar transport near lateral margins of the incipient primordium is critical for patterning leaf adaxial-abaxial axis,as blocking the transport by treatments with either auxin transport inhibitor or incisions caused abaxialized leaves.Our results also suggest that the previous incisions causing abaxailized leaves may disturb this auxin transport.We provide a model for how the auxin polar transport functions in patterning leaf adaxial-abaxial axis.