PIN6 auxin transporter at endoplasmic reticulum and plasma membrane mediates auxin homeostasis and organogenesis in Arabidopsis

Abstract

SummaryPlant development mediated by the phytohormone auxin depends on tightly controlled cellular auxin levels at its target tissue that are largely established by intercellular and intracellular auxin transport mediated by PIN auxin transporters. Among the eight members of the Arabidopsis PIN family, PIN6 is the least characterized candidate.In this study we generated functional, fluorescent protein-tagged PIN6 proteins and performed comprehensive analysis of their subcellular localization and also performed a detailed functional characterization of PIN6 and its developmental roles.The localization study of PIN6 revealed a dual localization at the plasma membrane (PM) and endoplasmic reticulum (ER). Transport and metabolic profiling assays in cultured cells and Arabidopsis strongly suggest that PIN6 mediates both auxin transport across the PM and intracellular auxin homeostasis, including the regulation of free auxin and auxin conjugates levels. As evidenced by the loss-and gain-of-function analysis, the complex function of PIN6 in auxin transport and homeostasis is required for auxin distribution during lateral and adventitious root organogenesis and for progression of these developmental processes.These results illustrate a unique position of PIN6 within the family of PIN auxin transporters and further add complexity to the developmentally crucial process of auxin transport.

Control of Arabidopsis lateral root primordium boundaries by MYB36

“…Thus, MYB36 is necessary before the transition from a flat to dome LRP, coinciding with the arrest of cell division to set the final width of the LRP. A highly localized expression domain in the LRP, similar to that of MYB36 , has been reported for other genes such as PIN6 , an intracellular auxin transporter (Benkova et al ., ; Simon et al ., ) and PUCHI , an auxin‐regulated AP2/EREB transcription factor (Hirota et al ., ) and several members of the RBOH family of oxidases (Orman‐Ligeza et al ., ). However, these genes are expressed earlier in LRP development and are likely not directly implicated in the flat LRP phenotype of myb36 mutants that we describe here.…”

Na+,K+/H+ antiporters regulate the pH of endoplasmic reticulum and auxin‐mediated development

“…In Arabidopsis , the PIN protein family consists of eight members that are divided into two groups: plasma membrane (PM)‐localized PINs and endoplasmic reticulum (ER)‐localized PINs (Viaene, Delwiche, Rensing, & Friml, ; Wabnik, Kleine‐Vehn, Govaerts, & Friml, ). The PM‐PINs contain PIN1‐PIN4 and PIN7, whereas the ER‐PINs contain PIN5, PIN6 (also acting at the PM; Simon et al, ), and PIN8. ER‐PINs mediate auxin transport between the ER lumen and the cytosol, and hence control auxin homeostasis of the cells (Adamowski & Friml, ; Friml & Jones, ; Grones & Friml, ).…”

“…PIN8 is significantly expressed in the male gametophyte and is crucial for pollen development (Dal Bosco et al, ; Ding et al, ). PIN6 is involved in nectar production, development of short stamens, and root growth and development acting at both the ER and PM (Bender et al, ; Cazzonelli et al, ; Simon et al, ). PIN5 functions in lateral root initiation and in root and hypocotyl growth (Mravec et al, ).…”

A Genome-Scale Analysis of the PIN Gene Family Reveals Its Functions in Cotton Fiber Development

“…AtPIN5 and AtPIN8, are localized in the endoplasmic reticulum and are involved in the homeostasis of intracellular auxin (Mravec et al, 2009; Ding et al, 2012). Interestingly, AtPIN6 is found to localize in both the plasma membrane and endoplasmic reticulum (Simon et al, 2016). Moreover, the PIN genes have been reported to be involved in the hormone signaling and abiotic stress responses, such as drought, salt and dehydration (Willige et al, 2011; Guo et al, 2015; Li F. et al, 2015).…”