Plasma Membrane-Targeted PIN Proteins Drive Shoot Development in a Moss

Abstract

SummaryBackgroundPlant body plans arise by the activity of meristematic growing tips during development and radiated independently in the gametophyte (n) and sporophyte (2n) stages of the life cycle during evolution. Although auxin and its intercellular transport by PIN family efflux carriers are primary regulators of sporophytic shoot development in flowering plants, the extent of conservation in PIN function within the land plants and the mechanisms regulating bryophyte gametophytic shoot development are largely unknown.ResultsWe have found that treating gametophytic shoots of the moss Physcomitrella patens with exogenous auxins and auxin transport inhibitors disrupts apical function and leaf development. Two plasma membrane-targeted PIN proteins are expressed in leafy shoots, and pin mutants resemble plants treated with auxins or auxin transport inhibitors. PIN-mediated auxin transport regulates apical cell function, leaf initiation, leaf shape, and shoot tropisms in moss gametophytes. pin mutant sporophytes are sometimes branched, reproducing a phenotype only previously seen in the fossil record and in rare natural moss variants.ConclusionsOur results show that PIN-mediated auxin transport is an ancient, conserved regulator of shoot development.

Auxin Produced by the Indole-3-Pyruvic Acid Pathway Regulates Development and Gemmae Dormancy in the Liverwort Marchantia polymorpha

“…This transport was later supported by the findings of Gaal et al (1982) and Maravolo (1976), who showed that 14 C-IAA is transported in an apical-basal and dorsal-ventral manner in the M. polymorpha thallus. Considering M. polymorpha has at least four PIN-FORMED (PIN) genes (Bennett et al, 2014a), these findings suggest PIN-mediated polar auxin transport is an important mechanism for gametophytic M. polymorpha development, as recently shown in the moss P. patens (Bennett et al, 2014b;Viaene et al, 2014). Our IAA measurements of different thallus tissues suggested IAA levels correlate well with pro YUC2:GUS expression but less well with pro TAA: GUS, as Mp-TAA is highly expressed only in the meristematic region and the base of gemma cups, with much weaker signal in the midrib and no signal in thallus margins.…”

Diversity of phyllotaxis in land plants in reference to the shoot apical meristem structure

“…Furthermore, in light of the fact that similar developmental impairments have been shown in some monocots [113][114][115][116][117] and that homologs of PIN genes have been identified in gymnosperms [118,119], it is generally thought that the auxin mechanism of phyllotaxis regulation may be universal throughout the seed plants. Sequencing analyses have suggested that PIN genes may be present in the seedless land plants as well [119], and PAT has been shown to be present in Physcomitrella [120] and Selaginella [121], indicating that the auxin mechanism of phyllotaxis formation may be common to all land-plant lineages. However, localization of PIN proteins in the plasma membranes in the seedless plants has to date only be confirmed in Physcomitrella [120].…”

“…Sequencing analyses have suggested that PIN genes may be present in the seedless land plants as well [119], and PAT has been shown to be present in Physcomitrella [120] and Selaginella [121], indicating that the auxin mechanism of phyllotaxis formation may be common to all land-plant lineages. However, localization of PIN proteins in the plasma membranes in the seedless plants has to date only be confirmed in Physcomitrella [120]. Notably, PAT has also been identified in Chara (Characeae, green alga) [122], which shares a common ancestor with land plants, although PIN proteins in Chara are localized in the endoplasmic reticulum [123,124].…”

Can mosses serve as model organisms for forest research?

“…The ancient pathways for auxin (Bennett et al 2014a(Bennett et al , 2014bFinet and Jaillais 2012;Paponov et al 2009), cytokinin (Lindner et al 2014;Pils and Heyl 2009;von Schwartzenberg et al 2007), and ethylene (Yasumura et al 2012) were investigated with respect to their corresponding transporters, biosynthesis, and signaling pathways. Further, moss is lacking essential characteristics of the classical gibberellin signaling pathway, although it responds to external gibberellin treatment (Vandenbussche et al 2007).…”