Mutation in Arabidopsis MOR1 gene impairs endocytosis in stamen filament cells and results in anther indehiscence

Xiaolei Liu,Xiaoyun Tan

doi:10.1007/s10725-021-00777-7

Abstract

Anther dehiscence is a crucial step for pollen grains release and male fertility. Filaments, which transport water, nutrients and hormones to the anthers, are important for anther dehiscence. In this study, we characterized the Arabidopsis MICROTUBULE ORGANIZATION 1 (MOR1) gene that involves in the filament functions and plays important roles in anther dehiscence. The Arabidopsis microtubule organization 1–1 (mor1-1) mutant exhibited an anther indehiscence phenotype at 24 °C. Such the defect did not occur at a lower temperature (19 °C). Further analysis indicated that both the cortical microtubule (CMT) organization and plasma membrane homeostasis were drastically impaired and disturbed in mor1-1 filament cells under the growth conditions of 24 °C. Transmission electron microscopy and FM4-64 up-take assays showed that endocytosis process in the mor1-1 filament cells were disrupted at 24 °C. Furthermore, the cortical-associated RFP tagged clathrin light chain foci were reduced in the mor1-1 filament cells. These results suggested that the MOR1 mediated CMT organization is important for clathrin-mediated endocytosis in the filament cells, and critical for anther dehiscence in thermosensitivity.

Highlights

The Arabidopsis flower consists of four concentric whorls of organs from center to edge: pistil, stamens, petals, and sepals (Smyth et al, 1990)
The cortical-associated clathrin light chain (CLC) foci were dramatically reduced in the mor1-1 filament epidermal cells. These results suggested that the microtubule organization 1 (MOR1)-mediated cortical microtubule (CMT) organization is important for clathrin-mediated endocytosis (CME) in the filament cells, which plays a prominent role in filament development and anther dehiscence
We found that when the mor1-1 mutant plants were grown at a moderate temperature of 24°C, they all had normal vegetative development and could produce normal inflorescence, but exhibited an extremely lower fertility

Summary

Introduction

The Arabidopsis flower consists of four concentric whorls of organs from center to edge: pistil, stamens, petals, and sepals (Smyth et al, 1990). A stamen comprises an anther in which pollen grains are produced, and a stalk-like filament which functions in transport of water, nutrients and phytohormones to the anther and plays important roles in pollination by influencing pollen dispersal (Scott et al, 2004). At the floral stage 13, the filaments elongate rapidly, and anthers dehisce to release the mature pollen grains onto the stigma for pollination and subsequent fertilization (Sanders et al, 1999; Wilson et al, 2011). Investigating the molecular mechanisms how the filaments involve in anther dehiscence will provide effective tools for control of male fertility useful for crop hybrid breeding. Little has been known about the molecular mechanisms that regulate transport of water, nutrients and phytohormones in the filaments

Methods

Results

Conclusion