Yeast two-hybrid interactions between Arabidopsis lyrata S Receptor Kinase and the ARC1 E3 ligase

Indriolo E, Goring DR

Plant Signal Behav 2016 May;

PMID: 27175603


Here we describe protein-protein interactions between signaling components in the conserved self-incompatibility pathway from Brassica spp. and Arabidopsis lyrata. Previously, we had demonstrated that ARC1 is necessary in A. lyrata for the rejection of self-pollen by the self-incompatibility pathway. The results described here demonstrate that A. lyrata ARC1 interacts with A. lyrata S Receptor Kinase (SRK1) in the yeast two-hybrid system. A. lyrata ARC1 also interacted with B. napus SRK910 illustrating that interactions in this pathway are conserved across species. Finally, we discuss how the more widely occurring interactions between SRK and ARC1-related family members may be modulated in vivo by expression and subcellular localization patterns resulting in a particular response.

RNA Silencing of Exocyst Genes in the Stigma Impairs the Acceptance of Compatible Pollen in Arabidopsis

Safavian D, Zayed Y, Indriolo E, Chapman L, Ahmed A, Goring DR

Plant Physiol. 2015 Dec;169(4):2526-38

PMID: 26443677


Initial pollen-pistil interactions in the Brassicaceae are regulated by rapid communication between pollen grains and stigmatic papillae and are fundamentally important, as they are the first step toward successful fertilization. The goal of this study was to examine the requirement of exocyst subunits, which function in docking secretory vesicles to sites of polarized secretion, in the context of pollen-pistil interactions. One of the exocyst subunit genes, EXO70A1, was previously identified as an essential factor in the stigma for the acceptance of compatible pollen in Arabidopsis (Arabidopsis thaliana) and Brassica napus. We hypothesized that EXO70A1, along with other exocyst subunits, functions in the Brassicaceae dry stigma to deliver cargo-bearing secretory vesicles to the stigmatic papillar plasma membrane, under the pollen attachment site, for pollen hydration and pollen tube entry. Here, we investigated the functions of exocyst complex genes encoding the remaining seven subunits, SECRETORY3 (SEC3), SEC5, SEC6, SEC8, SEC10, SEC15, and EXO84, in Arabidopsis stigmas following compatible pollinations. Stigma-specific RNA-silencing constructs were used to suppress the expression of each exocyst subunit individually. The early postpollination stages of pollen grain adhesion, pollen hydration, pollen tube penetration, seed set, and overall fertility were analyzed in the transgenic lines to evaluate the requirement of each exocyst subunit. Our findings provide comprehensive evidence that all eight exocyst subunits are necessary in the stigma for the acceptance of compatible pollen. Thus, this work implicates a fully functional exocyst complex as a component of the compatible pollen response pathway to promote pollen acceptance.

The ARC1 E3 ligase promotes a strong and stable self-incompatibility response in Arabidopsis species: response to the Nasrallah and Nasrallah commentary

Goring DR, Indriolo E, Samuel MA

Plant Cell 2014 Oct;26(10):3842-6

PMID: 25336510


Following the identification of the male (S-locus Cysteine Rich/S-locus Protein 11) and female (S Receptor kinase [SRK]) factors controlling self-incompatibility in the Brassicaceae, research in this field has focused on understanding the nature of the cellular responses activated by these regulators. We previously identified the ARM Repeat Containing1 (ARC1) E3 ligase as a component of the SRK signaling pathway and demonstrated ARC1’s requirement in the stigma for self-incompatible pollen rejection in Brassica napus, Arabidopsis lyrata, and Arabidopsis thaliana. Here, we discuss our findings on the role of ARC1 in reconstructing a strong and stable A. thaliana self-incompatibility phenotype, in the context of the putative issues outlined in a commentary by Nasrallah and Nasrallah. Additionally, with their proposed standardized strategy for studying self-incompatibility in A. thaliana, we offer our perspective on what constitutes a strong and stable self-incompatibility phenotype in A. thaliana and how this should be investigated and reported to the greater community.