Illumina-based analysis of the rhizosphere microbial communities associated with healthy and wilted Lanzhou lily (<Emphasis Type="Italic">Lilium davidii</Emphasis> var. <Emphasis Type="Italic">unicolor</Emphasis>) plants grown in the field

Lanzhou lily (Liliumdavidii var. unicolor) is the best edible lily as well as a traditional medicinal plant in China. The microbes associated with plant roots play crucial roles in plant growth and health. However, little is known about the differences of rhizosphere microbes between healthy and wilted Lanzhou lily (Lilium davidii var. unicolor) plants. The objective of this study was to compare the rhizosphere microbial community and functional diversity of healthy and wilted plants, and to identify potential biocontrol agents with significant effect. Paired end Illumina Mi-Seq sequencing of 16S rRNA and ITS gene amplicons was employed to study the bacterial and fungal communities in the rhizosphere soil of Lanzhou lily plants. BIOLOG technology was adopted to investigate the microbial functional diversity. Our results indicated that there were major differences in the rhizosphere microbial composition and functional diversity of wilted samples compared with healthy samples. Healthy Lanzhou lily plants exhibited lower rhizosphere-associated bacterial diversity than diseased plants, whereas fungi exhibited the opposite trend. The dominant phyla in both the healthy and wilted samples were Proteobacteria and Ascomycota, i.e., 34.45 and 64.01 %, respectively. The microbial functional diversity was suppressed in wilted soil samples. Besides Fusarium, the higher relative abundances of Rhizoctonia, Verticillium, Penicillium, and Ilyonectria (Neonectria) in the wilted samples suggest they may pathogenetic root rot fungi. The high relative abundances of Bacillus in Firmicutes in healthy samples may have significant roles as biological control agents against soilborne pathogens. This is the first study to find evidence of major differences between the microbial communities in the rhizospheric soil of healthy and wilted Lanzhou lily, which may be linked to the health status of plants.     

Development of functional modules based on co-expression patterns for cell-wall biosynthesis related genes in rice

The functional elucidation of plant cell wall biosynthesis (CWB) related genes is important for understanding various stress tolerance responses as well as enhancing biomass in plants. Despite their significant role in physiology and growth of the plant, the function of a limited number of CWB related genes have been identified. Major obstacles such as functional redundancy and limited functional information pose challenges in the characterization of CWB genes. Here, a genome-wide analysis of CWB genes using meta-expression data revealed their roles in stress tolerance and developmental processes. The identification of coexpressed CWB genes suggests functional modules for plant cell wall biosynthesis associated with specific tissue types, biotic stress, abiotic stress, and hormone responses. More interestingly, we identified that glycosyl hydrolases are specialized for root and pollen development, glycosyltransferases for ubiquitous function and leaf development, and carbohydrate esterases for pollen development. A T-DNA insertional mutant of OsCESA9 showing internode preferred expression revealed severe dwarfism and a co-expression network analysis of OsCESA9 in oscesa9 mutant suggest downstream pathways for secondary cell wall biosynthesis and DNA repair processes. Data from our studies will facilitate functional genomic studies of CWB genes in rice and contribute to the enhancement of biomass and yield in crop plants.     

Overexpression of <Emphasis Type="Italic">MeDREB1D</Emphasis> confers tolerance to both drought and cold stresses in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis>

Cassava (Manihot esculenta) is an important tropical crop with extraordinary tolerance to drought stress but few reports on it. In this study, MeDREB1D was significantly and positively induced by drought stress. Two allelic variants of the gene named MeDREB1D(R-2) and MeDREB1D(Y-3) were identified. Overexpressing MeDREB1D(R-2) and MeDREB1D(Y-3) in Arabidopsis resulted in stronger tolerance to drought and cold stresses. Under drought stress, transgenic plants had more biomass, higher survival rates and less MDA content than wild-type plants. Under cold stress, transgenic plants also had higher survival rates than wild-type plants. To further characterize the molecular function of MeDREB1D, we conducted an RNA-Seq analysis of transgenic and wild-type Arabidopsis plants. The results showed that the Arabidopsis plants overexpressing MeDREB1D led to changes in downstream genes. Several POD genes, which may play a vital role in drought and cold tolerance, were up-regulated in transgenic plants. In brief, these results suggest that MeDREB1D can simultaneously improve plant tolerance to drought and cold stresses.