AUTHOR=Forestan Cristian , Farinati Silvia , Varotto Serena 

TITLE=The Maize PIN Gene Family of Auxin Transporters

JOURNAL=Frontiers in Plant Science

VOLUME=3

YEAR=2012

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2012.00016

DOI=10.3389/fpls.2012.00016

ISSN=1664-462X

ABSTRACT=<p>Auxin is a key regulator of plant development and its differential distribution in plant tissues, established by a polar cell to cell transport, can trigger a wide range of developmental processes. A few members of the two families of auxin efflux transport proteins, PIN-formed (PIN) and P-glycoprotein (ABCB/PGP), have so far been characterized in maize. Nine new <italic>Zea mays</italic> auxin efflux carriers <italic>PIN</italic> family members and two maize <italic>PIN-like</italic> genes have now been identified. Four members of <italic>PIN1</italic> (named <italic>ZmPIN1a–d</italic>) cluster, one gene homologous to <italic>AtPIN2</italic> (<italic>ZmPIN2</italic>), three orthologs of <italic>PIN5</italic> (<italic>ZmPIN5a</italic>–<italic>c</italic>), one gene paired with <italic>AtPIN8</italic> (<italic>ZmPIN8</italic>), and three monocot-specific <italic>PINs</italic> (<italic>ZmPIN9</italic>, <italic>ZmPIN10a</italic>, and <italic>ZmPIN10b</italic>) were cloned and the phylogenetic relationships between early-land plants, monocots, and eudicots PIN proteins investigated, including the new maize PIN proteins. Tissue-specific expression patterns of the 12 maize <italic>PIN</italic> genes, 2 <italic>PIN-like</italic> genes and <italic>ZmABCB1</italic>, an ABCB auxin efflux carrier, were analyzed together with protein localization and auxin accumulation patterns in normal conditions and in response to drug applications. <italic>ZmPIN</italic> gene transcripts have overlapping expression domains in the root apex, during male and female inflorescence differentiation and kernel development. However, some <italic>PIN</italic> family members have specific tissue localization: <italic>ZmPIN1d</italic> transcript marks the L1 layer of the shoot apical meristem and inflorescence meristem during the flowering transition and the monocot-specific <italic>ZmPIN9</italic> is expressed in the root endodermis and pericycle. The phylogenetic and gene structure analyses together with the expression pattern of the <italic>ZmPIN</italic> gene family indicate that subfunctionalization of some maize PINs can be associated to the differentiation and development of monocot-specific organs and tissues and might have occurred after the divergence between dicots and monocots.</p>