Membrane-Bound RLCKs LIP1 and LIP2 Are Essential Male Factors Controlling Male-Female Attraction in Arabidopsis

107

137

Growing plant cells need to rigorously coordinate external signals with internal processes. For instance, the maintenance of cell wall (CW) integrity requires the coordination of CW sensing with CW remodeling and biosynthesis to avoid growth arrest or integrity loss. Despite the involvement of receptor-like kinases (RLKs) of the Catharanthus roseus RLK1-like (CrRLK1L) subfamily and the reactive oxygen species-producing NADPH oxidases, it remains largely unknown how this coordination is achieved. ANXUR1 (ANX1) and ANX2, two redundant members of the CrRLK1L subfamily, are required for tip growth of the pollen tube (PT), and their closest homolog, FERONIA, controls root-hair tip growth. Previously, we showed that ANX1 overexpression mildly inhibits PT growth by oversecretion of CW material, whereas pollen tubes of anx1 anx2 double mutants burst spontaneously after germination. Here, we report the identification of suppressor mutants with improved fertility caused by the rescue of anx1 anx2 pollen tube bursting. Mapping of one these mutants revealed an R240C nonsynonymous substitution in the activation loop of a receptor-like cytoplasmic kinase (RLCK), which we named MARIS (MRI). We show that MRI is a plasma membranelocalized member of the RLCK-VIII subfamily and is preferentially expressed in both PTs and root hairs. Interestingly, mri-knockout mutants display spontaneous PT and root-hair bursting. Moreover, expression of the MRI R240C mutant, but not its wild-type form, partially rescues the bursting phenotypes of anx1 anx2 PTs and fer root hairs but strongly inhibits wild-type tip growth. Thus, our findings identify a novel positive component of the CrRLK1L-dependent signaling cascade that coordinates CW integrity and tip growth.receptor-like kinase signaling | cell wall integrity | pollen tube | root hair | Arabidopsis

Section: Resultsmentioning

confidence: 93%

Receptor-like cytoplasmic kinase MARIS functions downstream of Cr RLK1L-dependent signaling during tip growth

Boisson-Dernier

Franck

Lituiev

et al. 2015

107

137

“…For scanning electron microscopy observations, the pistils were fixed in FAA solution (50% ethanol, 5% acetic acid, 3.7% formaldehyde) for 24 h and dehydrated with a series of ethanol solutions (30%, 50%, 70%, 85%, 95%, and 100%) (54). The pistils were subsequently CO 2 critical point-dried, coated with sputtering gold, and then observed using a scanning electron microscope (JSM-6360LV; JEOL).…”

Section: Methodsmentioning

confidence: 99%

Cyclic nucleotide-gated channel 18 is an essential Ca ²⁺ channel in pollen tube tips for pollen tube guidance to ovules in Arabidopsis

Gao

Wang

et al. 2016

137

108

In flowering plants, pollen tubes are guided into ovules by multiple attractants from female gametophytes to release paired sperm cells for double fertilization. It has been well-established that Ca2+ gradients in the pollen tube tips are essential for pollen tube guidance and that plasma membrane Ca2+ channels in pollen tube tips are core components that regulate Ca2+ gradients by mediating and regulating external Ca2+ influx. Therefore, Ca2+ channels are the core components for pollen tube guidance. However, there is still no genetic evidence for the identification of the putative Ca2+ channels essential for pollen tube guidance. Here, we report that the point mutations R491Q or R578K in cyclic nucleotide-gated channel 18 (CNGC18) resulted in abnormal Ca2+ gradients and strong pollen tube guidance defects by impairing the activation of CNGC18 in Arabidopsis. The pollen tube guidance defects of cngc18-17 (R491Q) and of the transfer DNA (T-DNA) insertion mutant cngc18-1 (+/−) were completely rescued by CNGC18. Furthermore, domain-swapping experiments showed that CNGC18’s transmembrane domains are indispensable for pollen tube guidance. Additionally, we found that, among eight Ca2+ channels (including six CNGCs and two glutamate receptor-like channels), CNGC18 was the only one essential for pollen tube guidance. Thus, CNGC18 is the long-sought essential Ca2+ channel for pollen tube guidance in Arabidopsis.

“…Semi-in vivo pollen germination assay and aniline blue staining were conducted according to previously reported protocols (39). The histochemical GUS assay was performed according to a reported protocol (40).…”

Section: Methodsmentioning

confidence: 99%

AtVPS41-mediated endocytic pathway is essential for pollen tube–stigma interaction in Arabidopsis

Hao

Liu

Zhong

et al. 2016

Self Cite

In flowering plants, extensive male–female interactions are required for successful fertilization in which various signaling cascades are involved. Prevacuolar compartments (PVC) and vacuoles are two types of subcellular compartments that terminate signal transduction by sequestrating signaling molecules in yeast and mammalian cells; however, the manner in which they might be involved in male–female interactions in plants is unknown. In this study, we identified Arabidopsisthaliana vacuolar protein sorting 41 (AtVPS41), encoded by a single-copy gene with sequence similarity to yeast Vps41p, as a new factor controlling pollen tube–stigma interaction. Loss of AtVPS41 function disrupted penetration of pollen tubes into the transmitting tissue and thus led to failed male transmission. In the pollen tubes, AtVPS41 protein is associated with PVCs and the tonoplast. We demonstrate that AtVPS41 is required for the late stage of the endocytic pathway (i.e., endomembrane trafficking from PVCs to vacuoles) because internalization of cell-surface molecules was normal in the vps41-deficient pollen tubes, whereas PVC-to-vacuole trafficking was impaired. We further show that the CHCR domain is required for subcellular localization and biological functioning of AtVPS41. These results indicate that the AtVPS41-mediated late stage of the endocytic pathway is essential for pollen tube–stigma interaction in Arabidopsis.