SPECIFIC POLLEN EXTENSINS LRX ARE REQUIRED FOR MAINTAINING CELL WALL INTEGRITY DURING POLLEN TUBE GROWTH IN ARABIDOPSIS THALIANA

BORASSI, CECILIA; MUSCHIETTI, JORGE P.; WENGIER, DIEGO L.; SEDE, ANA R.; ESTEVEZ, JOSÉ M.

Córdoba

Congreso; XXXII Reunión Argentina / XVI Congreso Latinoamericano de FISIOLOGÍA VEGETAL; 2018

Polarized growth of pollen tubes is an oscillatory mechanismthat involves a tight coordination of Ca2+ions and Reactive Oxygen Species (ROS) with high traffickingof vesicles to the tip where a constant remodelingof the cell wall occurs. During this process, it iscrucial the regulatory and structural role of the cell walland the presence of glycoproteins and homogalacturonanswhich are involved in cell wall crosslinking contributingto maintain its proper assembly. Here, westudied the function of 4 pollen specific LRX8-11 (Leucine-rich Repeat Extensin-like) proteins which belongto the HRGP (Hydroxyproline-rich glycoprotein) familyin Arabidopsis thaliana. These chimeric proteins havean N-terminal LRR (Leucine-rich repeat) domain and aC-terminal extensin (EXT)-like domain with Ser-Pro repetitionspossibly glycosylated. The analysis of simple,double and one triple LRX knock-out mutants revealedan important reduction in pollen germination rates anda skewed segregation ratio due to defects in pollentransmission. We also found severe abnormalities inpollen tube morphology with the concomitant anomalousdeposition of pectin and callose at the cell wall.All together these results suggest that pollen LRX(8-11) are necessary to maintain cell wall integrity andprevent tip bursting during pollen germination and polarizedgrowth of pollen tubes.