Functional study of leucine-rich repeat extensins (LRXs) and prolyl-4-hydroxylases (P4Hs) during pollen tube growth

SEDE, ANA R.; MECCHIA, MARTIN A.; WENGIER, DIEGO L.; MUSCHIETTI, JORGE P.; BORASSI, CECILIA; ESTEVEZ, JOSE M.

buenos aires

Simposio; 3er Simposio Argentino de Glicobiología - GLYCOAR 2019; 2019

Polarized growth of pollen tubes implicates the constantremodeling of the cell wall at the apical region. The presence ofpolysaccharides and structural proteins such as Hydroxyprolinerichglycoproteins (HRGPs) involved in the crosslinking at the cellwall is crucial to maintain cell wall integrity. One of the membersof HRGP family are the leucine-rich repeat extensins (LRXs)which contain a leucine-rich repeat N-terminal domain and a Cterminalextensin domain with several Ser(Pro)3-5 repetitionsplausible to be glycosylated. In this study, we demonstrated thatpollen specific LRXs, LRX8-LRX11, are necessary to maintainthe correct assembly of the cell wall during polarized growth ofpollen tubes. We observed that the lack of LRX8-LRX11 affectspollen germination, the cell wall integrity of pollen tubes andalters mendelian inheritance. Moreover, loss of function triplemutant lrx9 lrx10 lrx11 pollen tubes displayed an overaccumulation of pectin and callose at the cell wall. Since prolinehydroxylation of extensins is necessary to define future Oglycosylationsites, we aimed to study the function of two pollenspecific enzymes from the prolyl-4-hydroxylase (P4H) family,P4H4 and P4H6. Our results showed a decrease in pollengermination of loss of function p4h4 and p4h6 mutants as well asby blocking P4Hs activity with specific P4H inhibitors. Finally, weobserved that P4H4 localized in the endoplasmic reticulum/Golgiapparatus of growing pollen tubes. Additional analysis will berequired to study the relevance of the hydroxylation over pollenstructural HRGPs proteins, specifically the functionalinvolvement of P4H4 and P4H6 in the hydroxylation of pollenLRXs.