ENDOPHYTIC AND RHIZOSPHERE MICROORGANISMS OF FIELD PENNYCRESS (THLASPI ARVENSE L.) PROMOTE PLANT ROBUSTNESS AND ARE ASSOCIATED WITH PLANT GENES MEDIATING PLANT-MICROBE INTERACTIONS

Andrew Spishakoff

Plants, both agricultural and wild-growing, form a plethora of mutualistic relationships with environmental microorganisms. These have been demonstrated to provide a wide array of benefits to their plant hosts. These benefits include improved access to nutrients, greater resistance to disease, and the lessening of the effects of abiotic stress. These benefits are achieved through a variety of biochemical mechanisms. Many mutualistic fungi and bacteria supply key nutrients such as nitrogen (N) and phosphorus (P) to associated plant hosts. The production of microbial metabolites such as exopolysaccharides and siderophores have been demonstrated to prevent damage caused by a lack of water and to protect host plants from metal toxicity. The production of phytohormones by mutualistic organisms also has a measurable positive impact on hosts and has been demonstrated to impact aboveground community diversity and plant immune responses. These associations are engaged by complex molecular communication between plants and microbes. While these benefits to plants are well documented the continued stochasticity of these communities renders these advantages difficult to replicate. A potential avenue to stabilize microbial communities for reliable associations is the utilization of seed-associated microorganisms, those passed from generation to generation in the microbiome of plant seeds. Seed endophytes play a strong role in the initial microbiome of plants and must participate in a variety of molecular communication systems to circumvent plant immunity and gain access to plant seeds. By using field pennycress, an emerging oilseed crop, seed endophytes were tested for plant growth promoting characteristics. Additionally, 16S and ITS amplicons were correlated to SNPs in the pennycress genome to elucidate genetic mechanisms of association between community composition and pennycress as the host plant. This analysis confirmed the presence of PGP microorganisms inhabiting the pennycress seed endosphere. Taxa were also correlated to SNPs in the pennycress genome aligned to genes typically involved in plant-microbe symbiosis. Prediction of KEGG orthologies and subsequent analysis displayed enrichment of receptors for known plant-microbe communication molecules. Organisms significantly enriched in the seed endosphere were also less impacted by experimental sites (climate and soil differences) and highly heritable, indicating strong symbiosis between pennycress and a small number of its holobiont organisms.

ENDOPHYTIC AND RHIZOSPHERE MICROORGANISMS OF FIELD PENNYCRESS (THLASPI ARVENSE L.) PROMOTE PLANT ROBUSTNESS AND ARE ASSOCIATED WITH PLANT GENES MEDIATING PLANT-MICROBE INTERACTIONS

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