STUDY OF RALF4/19 PEPTIDES ROLE DURING POLLEN TUBE GROWTH IN ARABIDOPSIS THALIANA.

SOMOZA SC; BOCCARDO NA; SEDE AR; WENGIER DL; MUSCHIETTI JP

Salta

Congreso; Joint XIV PABMB Congress and LV Annual SAIB Meeting; 2019

Polarized cell growth involves the expansion of one of its ends, making a cell elongate in a single direction. In plants, this process occurs in growing pollen tubes, root hairs and cotton fibers and is regulated by cytoskeletal reorganization, vesicular movement, Ca 2+ and reactive oxygen species (ROS) signaling. Polarized cell growth requires the synthesis and deposition of an extracellular layer rigid enough to withstand substantial internal turgor pressure, but at the same time flexible enough to permit the cell to grow.RAPID ALKALINIZATION FACTORs (RALFs) are secreted peptides relevant for transducing extracellular signals to the inside of the cell. With 36 members in Arabidopsis thaliana, RALFs regulate diverse developmental andphysiological processes. In particular, RALFs are known for inhibit cell elongation. Eight Arabidopsis RALFs are expressed in pollen and we focused our study on two of them, RALF4 and RALF19, closely related to each other. RALF4 and RALF19 are required to maintain proper pollen tube growth, through the interaction with LEUCINE- REICH EXTENSIN (LRXs) and Catharanthus roseus receptor-like kinases (CrRLK1Ls) proteins. This interaction regulates changes in the integrity of pollen tube cell wall transmitting this signal to the interior of the pollen tube. At the end of the journey, a pistil RALF (RALF34) triggers pollen tubes burst in order to release the sperm cells for fertilization, suggesting that regulation must be different at this point.Understanding of how these complexes regulate pollen tube growth will shed some light about how plantreproduction works.