The use of microbes in agriculture for enhancing crop production is an emerging alternative to chemical fertilizers and pesticides; however, their effectiveness is often limited by factors such as host genotype and variability in geographic location. To address this issue, the microbiomes of six different rice (Oryza sativa) seeds, sourced from two locations in Arkansas, U.S.A. of two different genotypes and two harvest years, were characterized. The bacterial and fungal communities were identified in each of four seed compartments (grain, outer grain, husk, and outer husk) using high throughput Illumina MiSeq sequencing. More unique amplicon sequence variants were identified in the outer seed husk and least in the grain compartment for both the fungal and bacterial microbiomes, however this only resulted in a decrease in diversity for the fungal communities. Principal component analysis indicated that each tissue compartment harbored relatively distinct bacterial and fungal communities for the three innermost compartments. A bacterial and fungal core microbiome shared among the six seed types for each compartment was identified. Key bacterial genera in the core across all compartments were Sphingomonas, Methylobacterium, and taxa in the family Enterobacteriaceae, members of which have been reported to support rice growth. Compared with the bacterial core, more fungal taxa were identified, possibly resulting from the more abundant reads after filtering, and key genera identified were Alternaria, Hannaella, and members of the order Pleosporales. These core members represent valuable candidates for manipulating the rice microbiome, decreasing the use of chemicals while increasing plant performance.

RNA interference is a biological process whereby small RNAs inhibit gene expression through neutralizing targeted mRNA molecules. This process is conserved in eukaryotes. Here, recent work regarding the mechanisms of how small RNAs move within and between organisms is examined. Small RNAs can move locally and systemically in plants through plasmodesmata and phloem, respectively. In fungi, transportation of small RNAs may also be achieved by septal pores and vesicles. Recent evidence also supports bidirectional cross‐kingdom communication of small RNAs between host plants and adapted fungal pathogens to affect the outcome of infection. We discuss several mechanisms for small RNA trafficking and describe evidence for transport through naked form, combined with RNA‐binding proteins or enclosed by vesicles.

Microbes form close associations with host plants including rice as both surface (epiphytes) and internal (endophytes) inhabitants. Yet despite rice being one of the most important cereal crops agriculturally and economically, knowledge of its microbiome, particularly core inhabitants and any functional properties bestowed is limited. In this study, the microbiome in rice seedlings derived directly from seeds was identified, characterized and compared to the microbiome of the seed. Rice seeds were sourced from two different locations in Arkansas, USA of two different rice genotypes (Katy, M202) from two different harvest years (2013, 2014). Seeds were planted in sterile media and bacterial as well as fungal communities were identified through 16S and ITS sequencing, respectively, for four seedling compartments (root surface, root endosphere, shoot surface, shoot endosphere). Overall, 966 bacterial and 280 fungal ASVs were found in seedlings. Greater abundance and diversity were detected for the microbiome associated with roots compared to shoots and with more epiphytes than endophytes. The seedling compartments were the driving factor for microbial community composition rather than other factors such as rice genotype, location and harvest year. Comparison with datasets from seeds revealed that 91 (out of 296) bacterial and 11 (out of 341) fungal ASVs were shared with seedlings with the majority being retained within root tissues. Core bacterial and fungal microbiome shared across seedling samples were identified. Core bacteria genera identified in this study such as Rhizobium, Pantoea, Sphingomonas, and Paenibacillus have been reported as plant growth promoting bacteria while core fungi such as Pleosporales, Alternaria and Occultifur have potential as biocontrol agents.

The spaceflight environment of the International Space Station poses a multitude of stresses on plant growth including reduced gravity. Plants exposed to microgravity and other conditions on the ISS display root skewing, changes in gene expression and protein abundance that may result in changes in cell wall composition, antioxidant accumulation and modification of growth anisotropy. Systematic studies that address the effects of microgravity on cellular organelles are lacking but altered numbers and sizes of vacuoles have been detected in previous flights. The prominent size of plant vacuoles makes them ideal models to study organelle dynamics in space. Here, we used Arabidopsiszigzag-1 (zig-1) as a sensitized genotype to study the effect of microgravity on plant vacuole fusion. Wortmannin was used to induce vacuole fusion in seedlings and a formaldehyde-based fixation protocol was developed to visualize plant vacuole morphology after sample return, using confocal microscopy. Our results indicate that microgravity enhances the zig-1 phenotype by reducing hypocotyl growth and vacuole fusion in some cells. This study demonstrates the feasibility of chemical inhibitor treatments for plant cell biology experiments in space.

The spaceflight environment of the International Space Station poses a multitude of stresses on plant growth including reduced gravity. Plants exposed to microgravity and other conditions on the ISS display root skewing, changes in gene expression and protein abundance that may result in changes in cell wall composition, antioxidant accumulation and modification of growth anisotropy. Systematic studies that address the effects of microgravity on cellular organelles are lacking but altered numbers and sizes of vacuoles have been detected in previous flights. The prominent size of plant vacuoles makes them ideal models to study organelle dynamics in space. Here, we used Arabidopsis zigzag1 (zig-1) as a sensitized genotype to study the effect of microgravity on plant vacuole fusion. Wortmannin was used to induce vacuole fusion in seedlings and a formaldehyde-based fixation protocol was developed to visualize plant vacuole morphology after sample return, using confocal microscopy. Our results indicate that microgravity enhances the zig-1 phenotype by reducing hypocotyl growth and vacuole fusion in some cells. This study demonstrates the feasibility of chemical inhibitor treatments for plant cell biology experiments in space.