Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/5/2005
Publication Date: 6/5/2005
Citation: Chandran, D., Sharopova, N., Garvin, D.F., VandenBosch, K., Samac, D.A. 2005. Physiological and molecular examination of aluminum tolerance in Medicago truncatula [abstract]. 2005 Model Legume Congress, June 5-9, 2005, Pacific Grove, California. Abstract No. S11.
Technical Abstract: Aluminum (Al) toxicity is one of the important causes of crop losses in acid soils (pH<5). Under acidic conditions, several phytotoxic species of Al are released into the soil solution at levels that inhibit plant growth, ultimately resulting in plants impaired in water and mineral uptake. Decades of research in the area of Al tolerance has focused on monocots, while very limited research has been conducted in dicots and legumes in particular. Medicago truncatula is a model legume that shows synteny with agriculturally important legumes, such as alfalfa and soybean, and therefore is a good candidate for Al tolerance studies. Root growth was used as a measure of tolerance in a screen of 50 M. truncatula accessions resulting in the identification of an Al tolerant (T32) and sensitive accession (S70). An Al dose-response curve revealed a maximum difference in relative root growth between T32 and S70 in 2.5µM Al solutions, and data from time course experiments showed that relative root growth was almost 50% greater in T32 than S70 at all time points tested. Hematoxylin staining images showed complete Al exclusion from root tips of T32 in contrast to S70 by 24 h post Al exposure. Evan’s blue staining of T32 root tips revealed minor damage with cells of the outer layers sloughing off allowing for new growth at the root tip. However, in S70, the zone of damage was extensive with incomplete sloughing off of outer cell layers, allowing little new root tip growth. These data suggest that the Al tolerance of T32 may in part be due to its ability to eliminate the outer cell layers that are exposed to, and accumulate Al. To determine changes in gene expression that may be involved in such a response, long oligonucleotide micro-arrays were used to study Al-induced gene expression in T32 and S70 root tips at 12 h and 24 h post Al treatment. A cluster based analysis will be performed to identify suites of genes preferentially induced/repressed by Al in the tolerant accession.