Project description:Cercospora zeina is a fungal pathogen that causes gray leaf spot (GLS) disease on maize (Zea mays L.) in South Africa. Upon landing on a maize leaf, the pathogen rapidly enters through the stomata and continues to develop asymptomatically for up to 28 days before symptoms are seen. As previous work has yet to adequately determine how the pathogen behaves during its infective period, we used transcriptomics to gain insights about the in-planta development of the pathogen and explore how it uses its effectors to facilitate this process. Samples from B73 maize inbreds infected with C. zeina were harvested in a time course experiment and used for RNA sequencing. We used reads mapped to the C. zeina genome as a proxy for biomass accumulation. At the end of the latent period, C. zeina was found to rapidly accumulate biomass and showed a nearly 50-fold increase in biomass as symptoms appeared. There were two distinct transcriptional waves occurring across the infection period. The first wave showed expression of genes for cellular growth, maintenance and immune avoidance, whereas the second wave was enriched with genes involved in detoxification and carbohydrate catabolism. A total of 140 putative effector genes were differentially expressed over the time-courses, with most up-regulated during the mid stage when the switch to necrotrophy occurs. Transient expression of three of these C. zeina effectors (CzEcp2, CzNis1a, CzNis1b) induced plant immunity in Nicotiana spp. resulting in the development of a hypersensitive response. This suggests that a cohort of C. zeina effectors expressed at this time have functions for which receptors have evolved in non-host species like tobacco. Altogether, this work suggests C. zeina behaves as a latent necrotroph during infection and provides a foundation for future research into the infection biology of C. zeina on maize.
Project description:Maize kernel is an important source of food, feed and industrial raw materials. The illustration of the molecular mechanisms of maize kernel development will be helpful for the manipulation of maize improvements. Although a great many researches based on molecular biology and gecetics have greatly increased our understanding on the kernel development, many of the mechanisms controlling this important process remain elusive. In current study, a microarray with approximately 58,000 probes was used to study the dynamic gene expression during kernel development from the fertilization to physiological maturity. Samples from two consecutive time-points were paired and labeled using different fluorescent dyes (Cy3 and Cy5) and hybridized in the same array. Hybridization of slides was performed according to the manufacturer’s instructions (http://www.maizearray.org/). The hybridized slides were scanned by a Genepix 4000B (Axon, USA). A loop design was applied for running the microarray. Two replicates of each pair of samples were carried out to test both the reproducibility and quality of the chip hybridizations. By comparing six consecutive time-points, namely 1, 5, 10, 15, 25 and 35 days after pollination (DAP), 3,445 differentially expressed genes were identified. These genes were then grouped into 10 clusters showing specific expression patterns using a K-means clustering algorithm. An investigation of function and expression patterns of genes expanded our understanding of the regulation mechanism underlying the important developmental processes, cell division and kernel filling. The differential expression of genes involved in plant hormone signaling pathways suggested that phytohormone might play a critical role in the kernel developmental process. Moreover, regulation of some transcription factors and protein kinases might be involved in the whole developmental process. Keywords: Time course, development
Project description:Not much is known about the molecular processes involved during gravitropism in monocot plants such as maize. A microarray based study on the expression of genes after a gravity stimulating the maize pulvinus will provide us with valuable information and a better understanding of the underlying molecular processes involved in monocot gravitropism. Objectives for this study included the identification of genes that were regulated at the transcriptional and translation level during gravitropism in the maize pulvinus. This was achieved by microarray analysis of total RNA versus polyribosome associated RNA during a time-course of gravity stimulation of the maize pulvinus. Experiment Overall Design: Six week old maize plants were gravity stimulated by 90º reorientation. Upper (slow elongation) and lower (fast elongation) halves of the most gravity competent pulvini were harvested over a time course ranging from 2 minutes up to one hour (2min, 5 min, 15min, 30min, 60min). Pulvini samples from control (vertical, no gravity stimulation) plants were harvested and labeled as left and right. For each time point, total mRNA and polyribosome-associated mRNA were purified and the transcript profiles analyzed using Affymetrix GeneChip® Maize Genome Arrays. The experiment was repeated twice (two growing seasons) and represent two biological repetitions.
Project description:Strigolactones (SLs) are plant hormones that regulate diverse developmental processes and environmental responses in plants. It has been discovered that SLs play an important role in regulating plant immune resistance to pathogens, but there are currently no reports on their role in the interaction between Nicotiana benthamiana and Tobacco mosaic virus (TMV). In this study, the exogenous application of SLs weakened the resistance of N. benthamiana to TMV, promoting TMV infection, whereas the exogenous application of Tis108, an SL inhibitor, resulted in the opposite effect. Virus-induced gene silencing (VIGS) inhibition of two key SL synthesis enzyme genes, NtCCD7 and NtCCD8, enhanced the resistance of N. benthamiana to TMV. Additionally, we conducted a screening of N. benthamiana related to TMV infection. TMV-infected plants treated with SLs were compared to the control by using RNA-seq. KEGG enrichment analysis and weighted gene co-expression network analysis (WGCNA) of differentially expressed genes (DEGs) suggested that plant hormone signaling transduction may play a significant role in the SL-TMV-N. benthamiana interactions. This study reveals new functions of SLs in regulating plant immunity and provides a reference for controlling TMV diseases in production.
Project description:Compare gene expression between maize genotype resistant (Pa405) and susceptible (Oh28) to maize dwarf mosaic virus (MDMV) infection 4 days post-inoculation using microarrays.