Samuel, M. A. | bioRxiv Science

bioRxiv2020

Stigma Receptivity is controlled by Functionally Redundant MAPK Pathway Components in Arabidopsis

In angiosperms, the process of pollination relies on species-specific interaction and signaling between the male (pollen) and female (pistil) counterparts where the interplay between several pollen and stigma proteins decides the fate of the pollen. In Brassicaceae, the dry stigmatic papillary cells control pollen germination by releasing resources only to compatible pollen thereby allowing pollen to hydrate and germinate. Despite the identification of a number of stigmatic proteins that facilitate pollination responses, the signaling mechanisms that regulate functions of these proteins have remained unknown. Here we show that, in Arabidopsis, an extremely functionally redundant mitogen-activated protein kinase (MAPK) cascade is required for maintaining stigma receptivity to accept compatible pollen. Our genetic analyses demonstrate that in stigmas, five MAPK kinases (MKKs), MKK1/2/3/7/9 are required to transmit upstream signals to two MPKs, MPK3/4, to mediate compatible pollination. Compromised functions of these five MKKs in the quintuple mutant (mkk1/2/3RNAi/mkk7/9) phenocopied pollination defects observed in the mpk4RNAi/mpk3 double mutant. We further show that this MAPK nexus converges on Exo70A1, a previously identified stigmatic compatibility factor essential for pollination. Given that pollination is the crucial initial step during plant reproduction, understanding the mechanisms that govern successful pollination could lead to development of strategies to improve crop yield.

plant biology↗

bioRxiv2019

Progressive myoclonic epilepsy-associated gene Kctd7 regulates retinal neurovascular patterning and function

Neuron function relies on and instructs the development and precise organization of neurovascular units that in turn support circuit activity. However, our understanding of the molecular cues that regulate this relationship remains sparse. Using a high-throughput screening pipeline, we recently identified several new regulators of vascular patterning. Among these was the potassium channel tetramerization domain-containing protein 7 (KCTD7). Mutations in KCTD7 are associated with progressive myoclonic epilepsy, but how KCTD7 regulates neural development and function remains poorly understood. To begin to identify such mechanisms, we focus on mouse retina, a tractable part of the central nervous system that contains precisely ordered neuron subtypes supported by a trilaminar intravascular network. We find that deletion of Kctd7 results in defective patterning of the adult retina vascular network, resulting in increased branching, vessel length, and lacunarity. These alterations reflect early and specific defects in vessel development, as emergence of the superficial and deep vascular layers were delayed. These defects are likely due to a role for Kctd7 in inner retina neurons. Kctd7 it is absent from vessels but present in neurons in the inner retina, and its deletion resulted in a corresponding increase in the number of bipolar cells in development and increased vessel branching in adults. These alterations were accompanied by retinal function deficits. Together, these data suggest that neuronal Kctd7 drives growth and patterning of the vasculature and suggest that neurovascular interactions may participate in the pathogenesis of KCTD7-related human diseases.\n\nAlevy et al. Highlights O_LIKctd7 is required for normal retinal vascular organization and retinal function in adults.\nC_LIO_LIDeletion of Kctd7 disrupts the emergence of the superficial and deep vessel layers.\nC_LIO_LIKctd7 may impact vascular patterning through influencing neurons as it is expressed in and regulates bipolar cells.\nC_LIO_LIKctd7 driven neurovascular interactions may participate in the pathogenesis of KCTD7-related human diseases.\nC_LI\n\nLay SummaryNeuron function requires an organized vasculature to maintain brain health and prevent disease, but many neurovasculature regulatory genes remain unknown. Alevy et al. identify the progressive myoclonic epilepsy-associated gene Kctd7 as a key regulator of vascular development and retinal function. They further show that Kctd7 regulation of vessel patterning likely occurs downstream of its role in regulating the development or activity of specific neuron types. These data suggest that KCTD7-regulated neurovascular interactions may participate in the pathogenesis of associated human diseases.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC=\"FIGDIR/small/647008v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (37K):\norg.highwire.dtl.DTLVardef@176b8eorg.highwire.dtl.DTLVardef@1967120org.highwire.dtl.DTLVardef@1dcf4e5org.highwire.dtl.DTLVardef@151fce2_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗