The Arabidopsis USL1 controls multiple aspects of development by affecting late endosome morphology.

Rongrong Yuan,Genji Qin,Hao Yu,Yuxing Fang,Jingqiu Lan,Jiaying Huang,Jinzhe Zhang

doi:10.1111/nph.15249

Abstract

Summary The polar transport of auxin controls many aspects of plant development. However, the molecular mechanisms underlying auxin tranport regulation remain to be further elucidated.We identified a mutant named as usl1 (unflattened and small leaves) in a genetic screen in Arabidopsis thaliana. The usl1 displayed multiple aspects of developmental defects in leaves, embryogenesis, cotyledons, silique phyllotaxy and lateral roots in addition to abnormal leaves. USL1 encodes a protein orthologous to the yeast vacuolar protein sorting (Vps) 38p and human UV RADIATION RESISTANCE‐ASSOCIATED GENE (UVRAG). Cell biology, Co‐IP/MS and yeast two‐hybrid were used to identify the function of USL1.USL1 colocalizes at the subcellular level with VPS29, a key factor of the retromer complex that controls auxin transport. The morphology of the VPS29‐associated late endosomes (LE) is altered from small dots in the wild‐type to aberrant enlarged circles in the usl1 mutants. The usl1 mutant synergistically interacts with vps29. We also found that USL1 forms a complex with AtVPS30 and AtVPS34.We propose that USL1 controls multiple aspects of plant development by affecting late endosome morphology and by regulating the PIN1 polarity. Our findings provide a new layer of the understanding on the mechanisms of plant development regulation.

Highlights

The phytohormone auxin plays essential roles in control of many aspects of plant development from embryogenesis to postembryonic development as a morphogen by specific distribution through its biosynthesis, conjugation, metabolism and polar transport (Friml, 2003; Qin et al, 2005; Teale et al, 2006; Cheng et al, 2007; Baylis et al, 2013; Kazan, 2013; Bar & Ori, 2014; Kasprzewska et al, 2015; Tang et al, 2016)
Our findings suggest that USL1 controls plant development by forming a complex with AtVPS30 and AtVPS34 to regulate late endosome morphology
The T-DNA insertions disrupted the expression of At2g32760 in usl1-1 when we used the primer pair (F1 and R1) designed from the flanking sequences of T-DNA insertion site (Fig. 1e,f), because no specific bands were amplified

Summary

Introduction

The phytohormone auxin plays essential roles in control of many aspects of plant development from embryogenesis to postembryonic development as a morphogen by specific distribution through its biosynthesis, conjugation, metabolism and polar transport (Friml, 2003; Qin et al, 2005; Teale et al, 2006; Cheng et al, 2007; Baylis et al, 2013; Kazan, 2013; Bar & Ori, 2014; Kasprzewska et al, 2015; Tang et al, 2016). The asymmetric subcellular distribution of the PINFORMED (PIN) auxin transport family proteins generate local auxin gradients key for plant development by driving auxin to be transported from cell to cell in a polar manner (G€alweiler et al, 1998; Mu€ller et al, 1998; Tanaka et al, 2006). The changes of the PIN family proteins in subcellular organelles indirectly regulate plant development by affecting auxin distribution. PIN proteins undergo constitutive clathrin-mediated endocytosis to subsequently be recycled to different polar domains (Geldner et al, 2003; Dhonukshe et al, 2007; Tanaka et al, 2009; Feraru et al, 2012; Naramoto et al, 2014b) or to be delivered to vacuoles for degradation (Kleine-Vehn et al, 2008; Spitzer et al, 2009; Baster et al, 2013). PIN proteins on the plasma membrane (PM) can be internalized by membrane invagination to form clathrin-coated vesicles (CCVs). CCVs first reach the trans-Golgi network/early endosomes (TGN/EE)

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Discussion

Conclusion