The phytohormone auxin acts as a prominent signal, providing, by its local accumulation or depletion in selected cells, a spatial and temporal reference for changes in the developmental program [1][2][3][4][5][6][7] . The distribution of auxin depends on both auxin metabolism (biosynthesis, conjugation and degradation) [8][9][10] and cellular auxin transport [11][12][13][14][15] . We identified in silico a novel putative auxin transport facilitator family, called PIN-LIKES (PILS). Here we illustrate that PILS proteins are required for auxin-dependent regulation of plant growth by determining the cellular sensitivity to auxin. PILS proteins regulate intracellular auxin accumulation at the endoplasmic reticulum and thus auxin availability for nuclear auxin signalling. PILS activity affects the level of endogenous auxin indole-3-acetic acid (IAA), presumably via intracellular accumulation and metabolism. Our findings reveal that the transport machinery to compartmentalize auxin within the cell is of an unexpected molecular complexity and demonstrate this compartmentalization to be functionally important for a number of developmental processes.Prominent auxin carriers with fundamental importance during plant development are PIN-FORMED (PIN) proteins [1][2][3]6,9,15 . PIN1-type auxin carriers regulate the directional intercellular auxin transport at the plasma membrane. In contrast, atypical family member PIN5 regulates intracellular auxin compartmentalization into the lumen of the endoplasmic reticulum and its role in auxin homeostasis was recently identified 15,16 . PIN proteins have a predicted central hydrophilic loop, flanked at each side by five transmembrane domains. We screened in silico for novel PIN-like putative carrier proteins with a predicted topology similar to PIN proteins ( Fig. 1a and Supplementary Fig. 2) and identified a protein family of seven members (Fig. 1b) in Arabidopsis thaliana, which we designated as the PILS proteins. In contrast to the similarities in the predicted protein topology, PIN and PILS proteins do not show pronounced protein sequence identity (10-18%), which limits the identification of PILS proteins by conventional, reciprocal basic local alignment search tool (BLAST) approaches. However, the distinct PIN and PILS protein families contain both the InterPro auxin carrier domain which is an insilico-defined domain, aiming to predict auxin transport function (http://www.ebi.ac.uk/panda/InterPro.html). The PILS putative carrier family is conserved throughout the whole plant lineage, including unicellular algae (such as Ostreococcus tauri and Chlamydomonas reinhardtii) (Supplementary Fig. 3) where PIN proteins are absent 16 , indicating that PILS proteins are evolutionarily older.PILS genes are broadly expressed in various tissues (Fig. 1c) and PILS2-PILS7 were transcriptionally upregulated by auxin application in wild-type seedlings (Fig. 1d-f and Supplementary Fig. 4), indicating a role in auxin-dependent processes. To investigate the potential function of the putative PILS auxi...

Auxin is a key coordinative signal required for many aspects of plant development and its levels are controlled by auxin metabolism and intercellular auxin transport. Here we find that a member of PIn auxin transporter family, PIn8 is expressed in male gametophyte of Arabidopsis thaliana and has a crucial role in pollen development and functionality. Ectopic expression in sporophytic tissues establishes a role of PIn8 in regulating auxin homoeostasis and metabolism. PIn8 co-localizes with PIn5 to the endoplasmic reticulum (ER) where it acts as an auxin transporter. Genetic analyses reveal an antagonistic action of PIn5 and PIn8 in the regulation of intracellular auxin homoeostasis and gametophyte as well as sporophyte development. our results reveal a role of the auxin transport in male gametophyte development in which the distinct actions of ER-localized PIn transporters regulate cellular auxin homoeostasis and maintain the auxin levels optimal for pollen development and pollen tube growth.

Polar transport of the plant hormone auxin is controlled by PIN-and ABCB/PGP-efflux catalysts. PIN polarity is regulated by the AGC protein kinase, PINOID (PID), while ABCB activity was shown to be dependent on interaction with the FKBP42, TWISTED DWARF1 (TWD1). Using co-immunoprecipitation (co-IP) and shotgun LC-MS/MS analysis, we identified PID as a valid partner in the interaction with TWD1. Invitro and yeast expression analyses indicated that PID specifically modulates ABCB1-mediated auxin efflux in an action that is dependent on its kinase activity and that is reverted by quercetin binding and thus inhibition of PID autophosphorylation. Triple ABCB1/PID/TWD1 co-transfection in tobacco revealed that PID enhances ABCB1-mediated auxin efflux but blocks ABCB1 in the presence of TWD1. Phospho-proteomic analyses identified S634 as a key residue of the regulatory ABCB1 linker and a very likely target of PID phosphorylation that determines both transporter drug binding and activity. In summary, we provide evidence that PID phosphorylation has a dual, counter-active impact on ABCB1 activity that is coordinated by TWD1-PID interaction.

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Root gravitropism is a complex, plant-specific process allowing roots to grow downward into the soil. Polar auxin transport and redistribution are essential for root gravitropism. Here we summarise our current understanding of underlying molecular mechanisms and involved transporters that establish, maintain and redirect intercellular auxin gradients as the driving force for root gravitropism. We evaluate the genetic, biochemical and cell biological approaches presently used for the analysis of auxin redistribution and the quantification of auxin fluxes. Finally, we also discuss new tools that provide a higher spatial or temporal resolution and our technical needs for future gravitropism studies.

For cancer classification problems based on gene expression, the data usually has only a few dozen sizes but has thousands to tens of thousands of genes which could contain a large number of irrelevant genes. A robust feature selection algorithm is required to remove irrelevant genes and choose the informative ones. Support vector data description (SVDD) has been applied to gene selection for many years. However, SVDD cannot address the problems with multiple classes since it only considers the target class. In addition, it is time-consuming when applying SVDD to gene selection. This paper proposes a novel fast feature selection method based on multiple SVDD and applies it to multi-class microarray data. A recursive feature elimination (RFE) scheme is introduced to iteratively remove irrelevant features, so the proposed method is called multiple SVDD-RFE (MSVDD-RFE). To make full use of all classes for a given task, MSVDD-RFE independently selects a relevant gene subset for each class. The final selected gene subset is the union of these relevant gene subsets. The effectiveness and accuracy of MSVDD-RFE are validated by experiments on five publicly available microarray datasets. Our proposed method is faster and more effective than other methods.

Cadmium (Cd) is one of the most toxic heavy metals for plant growth in soil. ATP-binding cassette (ABC) transporters play important roles in biotic and abiotic stresses. However, few ABC transporters have been characterized in poplar. In this study, we isolated an ABC transporter gene PtoABCG36 from Populus tomentosa. The PtoABCG36 transcript can be detected in leaves, stems and roots, and the expression in the root was 3.8 and 2 times that in stems and leaves, respectively. The PtoABCG36 expression was induced and peaked at 12 h after exposure to Cd stress. Transient expression of PtoABCG36 in tobacco showed that PtoABCG36 is localized at the plasma membrane. When overexpressed in yeast and Arabidopsis, PtoABCG36 could decrease Cd accumulation and confer higher Cd tolerance in transgenic lines than in wild-type (WT) lines. Net Cd2+ efflux measurements showed a decreasing Cd uptake in transgenic Arabidopsis roots than WT. These results demonstrated that PtoABCG36 functions as a cadmium extrusion pump participating in enhancing tolerance to Cd through decreasing Cd content in plants, which provides a promising way for making heavy metal tolerant poplar by manipulating ABC transporters in cadmium polluted areas.

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