Truncation of a Protein Disulfide Isomerase, PDIL2-1, Delays Embryo Sac Maturation and Disrupts Pollen Tube Guidance inArabidopsis thaliana

Abstract

Pollen tubes must navigate through different female tissues to deliver sperm to the embryo sac for fertilization. Protein disulfide isomerases play important roles in the maturation of secreted or plasma membrane proteins. Here, we show that certain T-DNA insertions in Arabidopsis thaliana PDIL2-1, a protein disulfide isomerase (PDI), have reduced seed set, due to delays in embryo sac maturation. Reciprocal crosses indicate that these mutations acted sporophytically, and aniline blue staining and scanning electron microscopy showed that funicular and micropylar pollen tube guidance were disrupted. A PDIL2-1-yellow fluorescent protein fusion was mainly localized in the endoplasmic reticulum and was expressed in all tissues examined. In ovules, expression in integument tissues was much higher in the micropylar region in later developmental stages, but there was no expression in embryo sacs. We show that reduced seed set occurred when another copy of full-length PDIL2-1 or when enzymatically active truncated versions were expressed, but not when an enzymatically inactive version was expressed, indicating that these T-DNA insertion lines are gain-of-function mutants. Our results suggest that these truncated versions of PDIL2-1 function in sporophytic tissues to affect ovule structure and impede embryo sac development, thereby disrupting pollen tube guidance.

Isolation and Proteomic Characterization of the Arabidopsis Golgi Defines Functional and Novel Components Involved in Plant Cell Wall Biosynthesis

“…BiP, CRT, and members of the PDI/PDIL family are frequently referred to as ER-lumen resident protein chaperones (Galat and Metcalfe, 1995;Jelitto-Van Dooren et al, 1999;Frand et al, 2000;Wu et al, 2010a). For a number of years, the definition of these proteins as ER residents has been questioned (Turano et al, 2002), and while BiP, CRT, and several of the PDI members identified in this study have been localized by fluorescent protein to the ER (Eubel et al, 2008;Wang et al, 2008), it is interesting that localization by MS suggests a more ubiquitous distribution (Heazlewood et al, 2004;Jaquinod et al, 2007;Marmagne et al, 2007;Mitra et al, 2009). It has now been conclusively demonstrated that BiP and CRT cycle between the ER and cis-Golgi and that both BiP and PDI1-1 are transported to lytic vacuoles via the Golgi apparatus (Pimpl et al, 2006;Ondzighi et al, 2008).…”

Female gametophyte-controlled pollen tube guidance

“…A number of additional genes and proteins have been postulated to play a role in funicular and micropylar PT guidance in Arabidopsis [28][29][30][31][32][33]. However, the majority of the genes seem to be required for PT growth, and FG maturation thus plays a more indirect or no role for PT guidance.…”

Protein Disulfide Isomerase-2 of Arabidopsis Mediates Protein Folding and Localizes to Both the Secretory Pathway and Nucleus, Where It Interacts with Maternal Effect Embryo Arrest Factor

“…Insertional inactivation of the PDI5 gene hastens the onset of programmed cell death in embryos, preventing seed development. Alternatively, PDI11 is a strict ER resident that assists embryo sac maturation and pollen tube direction (Wang et al, 2008), but proteins interacting with PDI11 have not yet been identified.…”