Submitted to: Plant Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/12/2006
Publication Date: 9/1/2006
Citation: Bucciarelli, B., Hanan, J., Palmquist, D.E., Vance, C.P. 2006. A standardized method for analysis of Medicago truncatula phenotypic development. Plant Physiology. 142:207-219. Interpretive Summary: With the widespread use of gene chips to study gene expression in plants it is critical to have methods established by which experimental data from different laboratories across the world can be evaluated and compared. In the model plant Arabidopsis, standardized protocols and growth/developmental stages have been developed and these are used by all Arabidopsis researchers. In legumes no standardized protocols or developmental stage descriptions have been established. In this study we used the model legume plant Medicago truncatula to develop a standardized nomenclature for growth and development. By measuring Medicago growth and development under nutrient-sufficient conditions and nutrient-deficient conditions we were able to describe incremental steps in morphological development and ascribe each a standardized numerical code. The measurements were then incorporated into a mathematical model to describe Medicago growth. This research is important because it describes a standardized nomenclature to define Medicago growth and development. The use of this nomenclature will allow legume researchers across the world to compare gene chip results in their laboratory to that from other laboratories.
Technical Abstract: Medicago truncatula has become a model system to study legume biology. It is imperative that a detailed growth characterization of the most commonly used cultivar, line A17 of cv. Jemalong, be documented. A detailed growth analysis creates a basis to analyze phenotypic alterations due to genetic lesions or environmental stress and is essential to characterize gene function and its relationship to morphological development. We have documented morphological development of M. truncatula to characterize its temporal developmental growth pattern; developed a numerical nomenclature coding system that identifies stages in morphological development; tested the coding system to identify phenotypic differences under phosphorus (P) and nitrogen (N) deprivation; and created a developmental model to visualize comparisons. The numerical nomenclature coding system, based on a series of defined growth units, represents incremental steps in morphological development. Included is a decimal component defining growth-units into nine sub-stages. A measurement component helps distinguish alterations that may be missed by the coding system. Growth under N and P deprivation produced morphological alterations that were distinguishable using the coding system and its measurement component. N and P deprivation resulted in delayed leaf development and expansion; delayed axillary shoot emergence and elongation; decreased leaf and shoot size and altered root growth. Timing and frequency of flower emergence in P-deprived plants was affected. This numerical coding system may be used as a standardized method to analyze phenotypic variation in M. truncatula resulting from nutrient stress or other factors and should allow valid growth comparisons across geographically distant laboratories.