Ovule defects in Arabidopsis thaliana PIN localization pathway mutants lead to reduced seed set
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Date
2025
Authors
Reiter, Jaxon W.
University of Lethbridge. Faculty of Arts and Science
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Publisher
Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences
Abstract
Chapter 1:
Auxin is a plant hormone that is essential for a wide range of growth and developmental processes in plants. The coordinated, polar transport of auxin through plant tissues is crucial for proper development and function. The asymmetric localization of PIN-FORMED (PIN) proteins determines the directionality of auxin transport between cells and across a tissue, creating an auxin gradient that can influence gene expression and development. It is well known that auxin gradient establishment is vital for vegetative development, including leaf and root formation, but the involvement of auxin in reproductive development is less-well studied. The plasma-membrane localization of PIN proteins to direct auxin transport between cells is a critical process that involves a complex vesicle transport pathway and is regulated by a diverse set of genes. This review provides an overview of the current state of knowledge regarding the roles of PIN proteins during the development of the reproductive structures of a flower, the gynoecium and androecium, and describes some of the genes that have been proposed to function in this PIN localization pathway. Mainly, the importance of PIN1 localization and PIN1-mediated auxin transport for the development of the gynoecium, including the carpel tissue, ovary, ovules, and female gametophyte, is described in detail, emphasizing the importance of these processes during reproductive development in plants.
Chapter 2:
The formation of the gynoecium, including the stigma, style, transmitting tract, ovary, ovules, and female gametophytes requires the correct establishment of auxin gradients across a tissue directed by polar transport. PIN-FORMED (PIN) proteins are crucial for establishing local cellular auxin gradients that establish spatially organized auxin maxima and minima. PIN1 vesicle transport is tightly regulated by various genes that play a role in vesicle formation, transport, uncoating, and membrane localization. SCARFACE/VASCULAR NETWORK DEFECTIVE 3 (SFC/VAN3), FORKED1 (FKD1) & FORKED-LIKE (FL) Group 1 genes, COTYLEDON VASCULAR PATTERN 2 (CVP2) and CVP2-LIKE 1 (CVL1), PINOID (PID), and ROTUNDA3 (RON3) have all been proposed to be key players in the regulation of PIN1 vesicle trafficking. Mutations to these genes have been shown to disrupt PIN1 localization and lead to developmental defects such as impaired root development and vein formation. However, the role of these genes has not been previously characterized in gynoecium development, despite mutants showing severe reductions to seed set. This study examines the underlying causes of the seed set reductions present in fkd1/fl1-2/fl2/fl3, sfc-40, and cvp2/cvl1 mutants by analyzing reproductive development. Through manual pollination experiments, observation of pollen tube growth, and the analysis of ovule defects and pPIN1:PIN1-GFP expression during ovule development, I identified that reduced seed set in these mutants results from a gynoecium defect. Specifically, a reduced seed set involves altered ovule development, and I suggest that the observed morphological defects are consistent with alterations to PIN1 localization during early ovule development stages (2 ii-iii) in these mutants. This study suggests, for the first time, that SFC, FKD1, FL1, FL2, FL3, CVP2, and CVL1 play an important role in reproduction during ovule development.
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Keywords
auxin , floral development , PIN proteins , ovule development , Arabidopsis