The Stacey laboratory was recently awarded a four-year grant from the National Institutes of Health to continue their studies of purinergic signaling in plants.

Abstract

Purinergic signaling appears to be an ancient, conserved trait; for example, P2X receptors trace back one billion years in evolution. However, although virtually all organisms respond to extracellular ATP (eATP), canonical P2X and P2Y receptors appear absent in insects, roundworm, and higher plants. Our laboratory identified the first plant, purinergic receptor, DORN1, which defines a new receptor kinase family of purinoreceptors (P2K) (Choi et al. Science. 2014). This receptor mediates the primary signaling response to eATP, eliciting many responses that are comparable to an animal inflammatory response. Convergent evolution has resulted in different receptors for eATP in plants and animals but the question remains whether other components of the purinergic signaling pathway may be conserved. It is now apparent that purinergic signaling plays a variety of important roles in plants; again mirroring the diverse roles that eATP signaling plays in mammals. Experiments will be performed to further define the mechanism of DORN1 function, identifying downstream signaling components, discover and characterize additional plant purinergic receptors and identify additional components of the plant purinergic response pathway.  The ultimate goal will be a holistic and integrated view of plant purinergic signaling, beginning with the novel P2K receptors, with the definition of plant-specific and, more importantly, plant and animal conserved components. This comparative approach should broaden our knowledge of purinergic signaling in higher organisms.

A partnership between MU and Gyeongsang National University in South Korea has created lasting connections.

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By Eleanor Hasenbeck | Bond Life Sciences Center

Discussion went global this week as researchers converged from Gyeongsang National University in South Korea, MU and Washington University at Bond Life Sciences Center for the sixth MU-GNU International Joint Symposium on Plant Biotechnology.

Plant biologists from each university shared their research, ranging from molecular biology and signaling to breeding soybeans for improved yields. The symposium is held every two years, alternating locations between the U.S. and South Korea. This conference marks the eleventh year of collaboration between GNU and MU.

“Every trip that comes over, new collaborations develop,” said Gary Stacey, a Bond LSC scientist of soybean biotechnology and chair of the symposium’s local organizing committee. “Just at dinner the other night, you could hear people talking and saying ‘We should do that together.’ You get people together and they collide, and good things come from that. The whole idea of these symposiums is trying to increase those collisions.”

As those involved share new research and ideas, these collaborations create opportunities. A former student in Stacey’s lab recently received a doctoral degree from both universities as part of a joint-doctoral degree program. Undergraduate Korean students can also complete a “2+2” degree, where students can begin their studies with two years at GNU and finish with two years at MU.

The schools also exchange faculty members. GNU researchers Jong Chan Hong and Woo Sik Chung completed sabbaticals at MU. Stacey has spent time in Korea, and his lab receives funding from Korean grants.

“Getting our students to interact with Korean students and Korean faculty expands their horizons, gets them in contact with other cultures and is really part of creating an intellectual environment where students can grow,” Stacey said.

For Stacey, the symposium has also brought valued friendships. “After you’ve been over there, and you know these guys for eleven years, it’s like your cousin coming home,” he said. “You’re not a visitor anymore. You’re like part of the family.”

For more information about the science exchanged, visit https://staceylab.missouri.edu/symposium.

A group of students from the Stacey lab, including Nhung Hoang (first from left) and Adama (fourth from left) won the trivia contest at the Division of Plant Sciences banquet on May 3, 2017.

You can try the quiz using this Link.

Members of the Stacey Lab attending the Mizzou – Division of Plant Sciences Banquet 2017. Nhung Hoang (first from left), Prof. Gary Stacey (third from left), Adama (fourth form left), Prof. Bing Stacey (fifth from left).

Sterling Evans, an undergraduate student of plant sciences, received the best undergraduate award for his poster on “Phenotypic screening of the response of Setaria viridis to plant growth promoting bacteria” at the 33th Life Science Week at the University of Missouri, 10-14 April, 2017. Sterling has joined the Stacey lab since the Fall semester of 2016.

Figure. Sterling with his mentors at the poster award ceremony

Figure. Sterling is explaining his work to a judge

Arabidopsis E3 ubiquitin ligase PLANT U-BOX13 (PUB13) regulates chitin receptor LYSIN MOTIF RECEPTOR KINASE5 (LYK5) protein abundance

Liao D, Cao Y, Sun X, Espinoza C, Nguyen CT, Liang Y, Stacey G
 
Summary

Long-chain chitooligosaccharides are fungal microbe-associated molecular patterns (MAMPs) that are recognized by LYSIN MOTIF RECEPTOR KINASE5 (LYK5), inducing the formation of a complex with CHITIN ELICITOR RECEPTOR KINASE1 (CERK1). Formation of this complex leads to activation of the CERK1 intracellular kinase domain and induction of plant innate immunity in Arabidopsis.

We found that addition of chitooctaose induced LYK5 protein accumulation as a result of de novo gene expression and the inhibition of LYK5 protein degradation. Screening the putative E3 ligases for interaction with LYK5 identified PLANT U-BOX13 (PUB13), which complexed with LYK5, but this complex dissociated upon addition of chitooctaose. Consistent with these results, LYK5 protein abundance was higher in pub13 mutants compared with the wild-type without chitooctaose treatment, while similar abundance was detected with the addition of chitooctaose.

The pub13 mutants showed hypersensitivity to chitooctaose-induced rapid responses, such as the production of reactive oxygen species (ROS) and mitogen-activated protein (MAP) kinase phosphorylation, but exhibited normal responses to subsequent long-term chitooctaose treatment, such as gene expression and callose deposition. In addition, PUB13 could ubiquitinate the LYK5 kinase domain in vitro.

Taken together, our results suggest an important regulatory function for the turnover of LYK5 mediated by the E3 ligase PUB13.

Beverly received the 1st place in the poster competition at the MU DuPont Pioneer Symposium

We congratulate Beverly on receiving the 1st place in the poster competition at the First MU DuPont Pioneer Symposium, 2017. Her poster title is “In situ metabolic profiling of symbiotic soybean-rhizobia interactions by laser ablation – electrospray ionization mass spectrometry (LAESI – MS)”.

Poster Abstract

Plants synthesize specific compounds (e.g., metabolites) that are essential for biochemical processes, such as growth, development, and environmental response. Recent advancements in metabolomics have expanded and clarified plant biochemistry, genetics, and physiology under varying conditions. However, the spatiotemporal information about metabolite production, storage, and transport remains largely elusive. In recent years, Laser Ablation Electrospray Ionization Mass Spectrometry (LAESI-MS) has been implemented successfully in metabolite profiling of samples ranging from microalgae to plant tissues. This ambient MS technology allows sampling in native conditions, with minimal sample preparation, while preserving the spatial information of biomolecules. Here, we used LAESI-MS to investigate the metabolites in a well-characterized model plant-rhizobium system, specifically nitrogen-fixing soybean nodules resulting from root infection by Bradyrhizobium japonicum. This study demonstrates the feasibility of using LAESI-MS for the investigation into the plant-microbe symbiosis, as well as other plant processes.

Photo: Beverly in front of her poster during the poster competition session

Undergraduate students from Gyeongsang National University, Korea visited the Stacey Lab

Four undergraduate students from Gyeongsang National University visited the Stacey Lab on Friday, 20th January 2017 (photo). These students were selected for the 2016 Winter Global Pioneer Program GPP) from a contest involving 50 teams from different colleges and departments of Gyeongsang National University. The purpose of this program is to provide students opportunities to:

– Acquire global knowledge and opportunities for various cultural contacts through foreign educational and industrial activities.

– Cultivate students with pioneering spirit, challenging awareness and coping ability for changing global environment.

– Strengthen students’ globalization capabilities and promote Gyeongsang University through GPP activities.

Photo: Four undergraduate students from Gyeongsang National University visited the Stacey Lab (front row from left to right: Taeyoung Kim, Wonju Gwak, Hobin Kang, and Kyoungeun Kim; back row: Prof. Gary Stacey, Dr. Sung-Hwan Cho (post-doc), and Dr. Daewon Kim (post-doc).

Divergent cytosine DNA methylation patterns in single-cell, soybean root hairs

Md Shakhawat Hossain, Taiji Kawakatsu, Kyung Do Kim, Zhang Ning, Cuong T. Nguyen, Saad M. Khan, Josef M. Batek, Trupti Joshi, Jeremy Schmutz, Jane Grimwood, Robert J. Schmitz, Dong Xu, Scott A. Jackson, Joseph R. Ecker, Gary Stacey

Abstract

Chromatin modifications, such as cytosine methylation of DNA, play a significant role in mediating gene expression in plants, which affects growth, development, and cell differentiation. As root hairs are single-cell extensions of the root epidermis and the primary organs for water uptake and nutrients, we sought to use root hairs as a single-cell model system to measure the impact of environmental stress.

We measured changes in cytosine DNA methylation in single-cell root hairs as compared with multicellular stripped roots, as well as in response to heat stress.

Differentially methylated regions (DMRs) in each methylation context showed very distinct methylation patterns between cell types and in response to heat stress. Intriguingly, at normal temperature, root hairs were more hypermethylated than were stripped roots. However, in response to heat stress, both root hairs and stripped roots showed hypomethylation in each context, especially in the CHH context. Moreover, expression analysis of mRNA from similar tissues and treatments identified some associations between DMRs, genes and transposons.

Taken together, the data indicate that changes in DNA methylation are directly or indirectly associated with expression of genes and transposons within the context of either specific tissues/cells or stress (heat).

The Role of Plant Innate Immunity in the Legume-Rhizobium Symbiosis

(Annual Review of Plant Biology)

Yangrong Cao, Morgan K. Halane, Walter Gassmann, Gary Stacey

The nitrogen fixing rhizobium-legume symbiosis is considered mutualistic since both the plant host and bacterial symbiont appear to derive benefit: the plant host in the form of fixed nitrogen, which they can utilize for their metabolism, while the rhizobia gain a steady carbon supply and protected environment. Over time, rhizobial populations in the soil also increase in fields planted with legumes. A classic view of the evolution of mutualism is that it derives from an original pathogenic relationship, which attenuates over time to a situation in which both partners can derive benefit. If this is the case for rhizobia, then one might, for example, uncover features of the symbiosis that reflect this earlier pathogenic state. For example, similar to plant pathogens, it is now generally assumed that rhizobia actively suppress the host immune response, allowing infection and symbiotic establishment. Likewise, the host has retained mechanisms to control nutrient supply to the symbionts and to control the number of nodules formed so that they do not become too much of a burden. Recent results are uncovering the mechanistic details of how the plant innate immune system is induced and circumvented during rhizobial infection. For example, there is now clear evidence that rhizobia are initially recognized as pathogens and transiently activate immune responses. It is also apparent that, as is the case for plant pathogens, rhizobia secrete effector proteins that can actively suppress plant immunity. The open question is whether such events are strictly ancillary to the central symbiotic signaling pathway (e.g., that responding to the symbiotic Nod factor signal) or are in some unexplained way central to the ability of the rhizobia to infect their host. Subsequent to these early infection events, plant immune responses can also be induced inside the nodule, and likely play a role, for example, in nodule senescence. Thus, a balanced regulation of innate immunity is likely required throughout rhizobial infection, symbiotic establishment, and maintenance. In this review, we discuss the significance of plant immune responses in the regulation of symbiotic associations with rhizobia, as well as rhizobial avoidance of detection by the host immune system.