Location: Sunflower and Plant Biology ResearchTitle: Landscape features impact on soil available water, corn biomass, and gene expression during the late vegetative stage Author
Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2013
Publication Date: 5/17/2013
Citation: Hansen, S., Clay, S.A., Clay, D.E., Carlson, C.G., Reicks, G., Jarachi, Y., Horvath, D.P. 2013. Landscape features impact on soil available water, corn biomass, and gene expression during the late vegetative stage. The Plant Genome. 6(2):1-9. Interpretive Summary: This study examined the reasons why corn plants growing on a historically high yielding area (a backslope of a well studied field plot) did better than corn plants growing on a very nearby historically low yielding area (on the summit and shoulder of a hill in the same field). Soil samples and crop yield data were collected, and plant samples were taken to look for changes in gene expression that might provide clues as to why the differences in yield were regularly observed. Nutrient and moisture analysis of the soil indicated that contrary to assumptions, there was little difference between the two landscape features. Indeed, the low yielding plots had slightly better levels of some nutrients such as phosphates. Moisture levels of the soil however, suggested that the low-yielding plots may have been deficient in water. Gene expression data indicated that plants growing in low-yielding areas had lower expression of photosynthetic genes which is what is expected for drought-stressed plants, but increased expression in genes that are indicative of responses to drought stress was surprising not observed. Interestingly, lower expression of genes required for phosphate up-take was observed in the low-yielding plots suggesting that these plants were less capable of benefitting from the increased phosphate levels. Surprisingly, plants in the high yielding areas had higher levels of expression from genes associated with disease and insect attack. Combined, the data suggested possible way to increase the yield in the lower-yielding plots.
Technical Abstract: In rolling landscapes, plant available water can vary drastically by topographic location with growth impaired by too much water in footslope locations and too little water in summit locations. This study examined corn (Zea mays) gene expression and plant productivity differences between two landscape positions located in historically high (lower backslope) and moderate (summit/shoulder) yielding zones based on 8 years of yield monitor data. Growth characteristics and gene expression were determined at the V-12 growth stage in a year when water availability was low at the summit but adequate in the backslope due to scant growing season rainfall. Water-stressed plants had 16% less leaf area, biomass, and P uptake compared with nonstressed plants. Gene expression, based on microarray analyses, indicated water-stressed plants had 708 genes down-regulated and 399 genes up-regulated compared with plants from zones with adequate water. Gene set and sub-network enrichment analyses indicated numerous altered growth and developmental pathways and circadian rhythm responses between stressed and nonstressed plants. Nutrient uptake, wound recovery, pest resistance, and photosynthetic capacity were down-regulated pathways in water-stressed plants. These results suggest that low water availability in the summit/shoulder position reduced biomass by lowering photosynthesis, wound recovery, nutrient uptake capacities, and reducing resistance response to insect and disease stresses. Adding nutrients to water-stressed zones may not increase productivity due to reduced nutrient uptake capacity. However, reducing plant populations, to lessen demands on available soil water, and applying pesticides, to limit biotic stress, may ameliorate negative water stress responses.