Role of the Arabidopsis PIN6 auxin transporter in auxin homeostasis and auxin-mediated development.

Christopher I Cazzonelli,Eva Benkova,Marleen Vanstraelen,Josette Masle,Ulrike Mathesius,Gauri Tarle,Nazia Nisar,Barry J Pogson,Iain R Searle,Abby J Cuttriss,Sibu Simon,Ashley Carron-Arthur,Kuide Yin,Jiří Friml

doi:10.1371/journal.pone.0070069

Abstract

Plant-specific PIN-formed (PIN) efflux transporters for the plant hormone auxin are required for tissue-specific directional auxin transport and cellular auxin homeostasis. The Arabidopsis PIN protein family has been shown to play important roles in developmental processes such as embryogenesis, organogenesis, vascular tissue differentiation, root meristem patterning and tropic growth. Here we analyzed roles of the less characterised Arabidopsis PIN6 auxin transporter. PIN6 is auxin-inducible and is expressed during multiple auxin–regulated developmental processes. Loss of pin6 function interfered with primary root growth and lateral root development. Misexpression of PIN6 affected auxin transport and interfered with auxin homeostasis in other growth processes such as shoot apical dominance, lateral root primordia development, adventitious root formation, root hair outgrowth and root waving. These changes in auxin-regulated growth correlated with a reduction in total auxin transport as well as with an altered activity of DR5-GUS auxin response reporter. Overall, the data indicate that PIN6 regulates auxin homeostasis during plant development.

Highlights

The plant hormone auxin is involved in embryogenesis, organogenesis, vascular tissue differentiation, and hypocotyl and root elongation, as well as growth responses to environmental stimuli
These experimental findings were consistent with anatomical gene expression analysis performed using Genevestigator, which confirms that PIN6 is lowly expressed in most seedling tissues (Fig. S2A)
The pin6 loss-of-function and misexpression lines demonstrated that PIN6 in Arabidopsis plays important developmental and physiological roles

Summary

Introduction

The plant hormone auxin is involved in embryogenesis, organogenesis, vascular tissue differentiation, and hypocotyl and root elongation, as well as growth responses to environmental stimuli. Auxin is synthesized in the shoot, leaf tips as well as in the root apex, and transported to other parts of the plant. Auxin moves in a polar manner from cell to cell or through the phloem from source to sink tissues. Polar cell-to-cell auxin transport is mediated by carrier proteins of the AUX1 (Auxin resistant 1), LAX (like-AUX1), PGP (Phospho-glycoprotein) and PIN (pinformed) families [3]. While AUX1, LAX and certain PGP-type proteins are involved in auxin import [6,7,8], there are other PGPtype and PIN proteins that mediate auxin export from the cell [6,9]

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Results

Discussion

Conclusion