Combined activity of LACS1 and LACS4 is required for proper pollen coat formation in Arabidopsis

Abstract

SUMMARYVery long chain lipids are important components of the plant cuticle that establishes the boundary surface of aerial organs. In addition, these lipids were detected in the extracellular pollen coat (tryphine), where they play a crucial role in appropriate pollen-stigma communication. As such they are involved in the early interaction of pollen with the stigma. A substantial reduction in tryphine lipids was shown to compromise pollen germination and, consequently, resulted in male sterility. We investigated the role of two long-chain acyl-CoA synthetases (LACSs) in Arabidopsis with respect to their contribution to the production of tryphine lipids. LACS was shown to provide CoA-activated very long chain fatty acids (VLCFA-CoAs) to the pathways of wax biosynthesis. The allocation of sufficient quantities of VLCFA-CoA precursors should therefore be relevant to the generation of tryphine lipids. Here, we report on the identification of lacs1 lacs4 double knock-out mutant lines that were conditionally sterile and showed significant reductions in pollen coat lipids. Whereas the contributions of both LACS proteins to surface wax levels were roughly additive, their co-operation in tryphine lipid biosynthesis was clearly more complex. The inactivation of LACS4 resulted in increased levels of tryphine lipids accompanied by morphological anomalies of the pollen grains. The additional inactivation of LACS1 neutralized the morphological defects, decreased the tryphine lipids far below wild-type levels and resulted in conditionally sterile pollen.

The Role of Arabidopsis ABCG9 and ABCG31 ATP Binding Cassette Transporters in Pollen Fitness and the Deposition of Steryl Glycosides on the Pollen Coat

“…By contrast, studies on pollen coat lipids were mostly centered on pollen-stigma interactions, such as the self-incompatibility response and pollen hydration (Preuss et al, 1993;Piffanelli et al, 1998). However, it is becoming evident that the pollen coat is also involved in maintaining pollen viability under harsh environmental conditions, as can be deduced from the sensitivity of many pollen coatless mutants to arid conditions (Preuss et al, 1993;Jessen et al, 2011) and the hypersensitivity to UV light stress of several mutants with pollen deficient in flavonoids, a component of the pollen coat (Hsieh and Huang, 2007).…”

Apoplastic Diffusion Barriers in Arabidopsis

“…Because the composition and biosynthesis of polyesters has been previously discussed (Li-Beisson et al, 2013), we will provide an overview here. The polymers associated with pollen, such as sporopollenin and tryphine, have been previously discussed (Ariizumi and Toriyama, 2011;Jessen et al, 2011) and fall outside the scope of this chapter.…”

The Tomato MIXTA-like Transcription Factor Coordinates Fruit Epidermis Conical Cell Development and Cuticular Lipid Biosynthesis and Assembly

“…5). Orthologs to these genes have been shown to be required for normal cuticle development in Arabidopsis: AtLACS1, AtLACS2, and AtLACS4 (Schnurr et al, 2004;Jessen et al, 2011). Three CYP450s were identified: SlCYP77A1, SlCYP77A2, and SlCYP86A68 ( Fig.…”

“…Modification includes mid-and terminal-chain hydroxylation and CoA activation followed by transfer to a glycerol moiety. Enzymes responsible for these steps include long-chain acyl-CoA synthetases (LACSs; Schnurr et al, 2004;Jessen et al, 2011), oxidases (CYTOCHROME P450 86A [CYP86A] and CYP77A; Li-Beisson et al, 2009;Pinot and Beisson, 2011;Shi et al, 2013), and acyltransferases (GLYCEROL-3-PHOSPHATE SN-2-ACYLTRANSFERASEs [GPATs] and likely, DEFECTIVE IN CUTICULAR RIDGES [DCR]; Panikashvili et al, 2009;Rani et al, 2010;Yang et al, 2010Yang et al, , 2012. The resultant monoacylglycerols undergo extracellular transport and finally, polymerization to form the cutin matrix.…”