α2-COP is involved in early secretory traffic in Arabidopsis and is required for plant growth

Abstract

HighlightIn Arabidopsis α2-COP is required for plant growth, Golgi structure and subcellular localization of p24δ5, with its loss of function resulting in upregulation of the COPII subunit SEC31A.

Characterization of the role of several COPI complex isoforms during the early acceptance of compatible pollen grains inArabidopsis thaliana

“…The results presented here are the first study to examine the role of the COPI complex during compatible pollinations. In the instance of the a-COPI isoforms, we were able to demonstrate the role of the a1-COPI isoform during compatible pollinations in the stigma and that it may have a different role compared to that of the previously characterized a2-COPI isoform, which appears to play a much greater role in secretory traffic throughout development in A. thaliana (Gimeno-Ferrer et al 2017). Many of the other subunits, and their isoforms, were much less informative with more subtle phenotypes during the characterization of their roles during pollen-pistil interactions.…”

“…These phenotypes were likely discovered due to our focus on the role of this isoform a1-copi in the context of pollen-pistil interactions while previous characterizations of this line were reported to appear wild-type when grown vegetatively. Previously, when the a1-copi plants were compared to the a2-copi isoform loss of function mutants, the a1-copi plant did not show the a2-copi isoform's phenotype which had global defects in plant growth, resulting in smaller rosettes, stems and roots as well as other morphological problems in protein localization and the Golgi structure (Gimeno-Ferrer et al 2017). Under our growing conditions, the a1-copi plants appeared healthy and wild-type in both size and in overall morphology; these observations are consistent with previous studies of the same mutant line when a1-copi plants were compared to the a2-copi-1, a2-copi-2 and a2-copi-3 plants that showed the dwarf phenotype (Gimeno-Ferrer et al 2017).…”

“…Previously, when the a1-copi plants were compared to the a2-copi isoform loss of function mutants, the a1-copi plant did not show the a2-copi isoform's phenotype which had global defects in plant growth, resulting in smaller rosettes, stems and roots as well as other morphological problems in protein localization and the Golgi structure (Gimeno-Ferrer et al 2017). Under our growing conditions, the a1-copi plants appeared healthy and wild-type in both size and in overall morphology; these observations are consistent with previous studies of the same mutant line when a1-copi plants were compared to the a2-copi-1, a2-copi-2 and a2-copi-3 plants that showed the dwarf phenotype (Gimeno-Ferrer et al 2017). As the dwarf phenotypes and the impact on secretory pathway genes in the a2-copi plants would alter all aspects of plant growth, future experiments should focus on knocking down a2-COPI under as stigma specific promoter such as SLR1 driving a a2-COPI RNAi construct in the a1-copi background (Trick 1990).…”

“…With increased anterograde traffic in the papilla cell to deliver vesicles to the pollen contact point to enable pollen grain hydration, there would be increased retrograde traffic to maintain membrane balance in the system. Coat Protein II (COPII) vesicles are involved in the anterograde transport of protein out from the ER while the Coat protein 1 (COPI) coated vesicles are the mediators of intra-Golgi transport and retrograde transport from the Golgi back towards the endoplasmic reticulum (Ahn et al 2015;Brandizzi and Barlowe 2013;Gimeno-Ferrer et al 2017). In regards to the intra-Golgi transport of COPI vesicles the directionality of their transport is still a matter of debate; however, their role in retrograde transport is clear (Jackson et al 2012).…”

“…The a2-copi mutants had major defects in overall plant growth and morphology, and the Golgi structure was altered in addition to the subcellular localization of p24d5, a protein that has been shown to cycle between the ER and the Golgi, which also contains the dilysine motif that is recognized by a-COPI isoforms (Gimeno-Ferrer et al 2017).…”