Community Profiling of Seed Endophytes from the Pb-Zn Hyperaccumulator Noccaea caerulescens and Their Plant Growth Promotion Potential

Abstract

Endophytes within plants are known to be crucial for plant fitness, and while their presence and functions in many compartments have been studied in depth, the research on seed endophytes is still limited. This work aimed to characterize the seed endophytic and rhizospheric bacterial community of two Noccaea caerulescens Pb-Zn hyperaccumulator populations, growing on two heavy-metal-polluted sites in Belgium. Cultured representatives were evaluated for their potential to enhance seed germination and root length of the model species Arabidopsis thaliana. The results indicated that the community structure within the seed is conserved between the two locations, comprising mainly of Proteobacteria (seeds), and Actinobacteria in the bulk soil. Root length of A. thaliana was significantly increased when inoculated with Sphingomonas vulcanisoli. The results of this paper offer insights into the importance of the selection of the core seed endophytic microbiome and highlight the precarious symbiotic relationship they have with the plant and seed.

Plant-Growth-Promoting Bacteria

“…The results reported by Langill et al [18] demonstrated that the selection of the core seed endophytic microbiome is crucial for host-plant fitness, highlighting the precarious symbiotic relationship it has with both the plant and seed. They hypothesized that introducing seed endophytes from N. caerulescens to the seeds of A. thaliana would improve the germination and overall plant health and biomass when A. thaliana is forced to germinate in marginal conditions.…”

Endophyte Community Changes in the Seeds of Eight Plant Species following Inoculation with a Multi-Endophytic Bacterial Consortium and an Individual Sphingomonas wittichii Strain Obtained from Noccaea caerulescens

“…Understanding the functional significance of seed endophytes has gained prominence due to their potential contributions to plant health and productivity. Numerous studies have revealed the ability of seed endophytes to enhance nutrient acquisition [7], improve stress tolerance [4,8], and promote plant growth [9,10]. These beneficial effects are attributed to various mechanisms, including nitrogen fixation, phosphate solubilization, production of plant-growth-promoting substances, and modulation of the plant's immune system.…”

“…Noccaea caerulescens, a hyperaccumulator plant species, has garnered significant importance in the field of phytoremediation and ecological research, making it an ideal candidate for our resilient plant. This metallophyte exhibits an exceptional tolerance to and accumulation of heavy metals, particularly zinc, cadmium, and nickel, in its aboveground tissues [10]. Still, this plant is not only found in polluted areas but also has a strong presence in dry hillside meadows, gardens, bare ground, and forests [12].…”

“…Previous research has shown Sphingomonas wittichii to be a seed endophyte present in N. caerulescens [10]. This particular endophyte has piqued the interest of the scientific community due to its ability to degrade environmental pollutants, such as dioxins [14][15][16].…”

“…This particular endophyte has piqued the interest of the scientific community due to its ability to degrade environmental pollutants, such as dioxins [14][15][16]. In addition to the outstanding degradation properties that S. wittichii possesses, it also previously showed promise in increasing plant biomass [10]. Because it was one of the few endophytes isolated from N. caerulescens that was able to be grown in the lab and held promise for seed inoculation, it was chosen as the isolate to test for the seed inoculation potential of crops.…”