A Physcomitrella PIN protein acts in spermatogenesis and sporophyte retention

Abstract

Summary The auxin efflux PIN‐FORMED (PIN) proteins are conserved in all land plants and important players in plant development. In the moss Physcomitrella (Physcomitrium patens), three canonical PINs (PpPINA–C) are expressed in the leafy shoot (gametophore). PpPINA and PpPINB show functional activity in vegetative growth and sporophyte development. Here, we examined the role of PpPINC in the life cycle of Physcomitrella. We established reporter and knockout lines for PpPINC and analysed vegetative and reproductive tissues using microscopy and transcriptomic sequencing of moss gametangia. PpPINC is expressed in immature leaves, mature gametangia and during sporophyte development. The sperm cells (spermatozoids) of pinC knockout mutants exhibit increased motility and an altered flagella phenotype. Furthermore, the pinC mutants have a higher portion of differentially expressed genes related to spermatogenesis, increased fertility and an increased abortion rate of premeiotic sporophytes. Here, we show that PpPINC is important for spermatogenesis and sporophyte retention. We propose an evolutionary conserved way of polar growth during early moss embryo development and sporophyte attachment to the gametophore while suggesting the mechanical function in sporophyte retention of a ring structure, the Lorch ring.

Mutant phenotypes and comprehensive expression analyses reveal roles for CLAVATA in moss vegetative and reproductive development and fertility

“…The data presented here identify caulonemal apical cells, gametophore apical cells, the base of developing leaves, rhizoid tips and pre-egg and egg cells as regions of high PpRPK2 and PpCLV1 promoter activity, coinciding with previously identified sites of minimal auxin sensing (Thelander et al ., 2019; Landberg et al ., 2021). Moreover, PpPIN expression domains are similar to CLAVATA expression domains in leaves and reproductive tissues (Landberg et al ., 2013; Viaene et al ., 2014; Lüth et al ., 2023), and Pppin mutants have fertility defects (Bennett et al ., 2014; Lüth et al ., 2023), a phenotype shared by CLAVATA receptor mutants (Figures 3-5). Auxin synthesis is required for normal egg development, and biosynthetic Ppshi - 2 mutant eggs resemble Pprpk2 mutant eggs (Landberg et al ., 2013).…”

Phytochemical Exploration of Ceruchinol in Moss: A Multidisciplinary Study on Biotechnological Cultivation of Physcomitrium patens (Hedw.) Mitt.

“…The moss's unique developmental characteristics, particularly its dominant haploid phase, the gametophyte, comprising protonema and gametophore, provide an excellent context for investigating the complexities of plant reproduction and growth. Investigations into the regulatory mechanisms of cell differentiation, gametogenesis, and sporogenesis in this moss have provided insights that have broader relevance to plant development as well as its physiology and structure [12][13][14][15], its relationship against aggressors and with the outside [16,17]. In sum, P. patens has assumed a pivotal role as a model organism in the fields of evolutionary and developmental biology, bridging gaps in our comprehension of early terrestrial plant life.…”

Control of leaf development in the water fern Ceratopteris richardii by the auxin efflux transporter CrPINMa in the CRISPR/Cas9 analysis

“…Both streptophytes and chlorophyta possess PIN s, despite they diverged from each other 1.2 billion years ago [ 23 ]. The PAT has also been observed in both algae and mosses [ 24 , 25 ]. In ferns, PIN s can function for a rudimentary root gravitropism [ 26 ].…”