Preliminary characterisation of two pilot bioindicators for sulfur nutritinal status

Background Although much progress has been made in improving fertilization practices there remain considerable uncertainties about the persistence of nutrients in the soil and their actual availability to the plants. Developing specific bioassays based on the use of “sentinel plants” to quickly determine nutrient bioavailability and/or crop nutritional status, may represent a reliable and efficient strategy to obtain valuable, timely and low-cost information about changes in nutrient availability and nutritional requirement in a crop system. Methods Two Arabidopsis gene trapping lines in which two different portions of an intergenic region between At1g12030 and At1g12040 control the expression of the GUS reporter gene have been characterized for the reporter specific responses to sulfur. Results The main results of this study showed that the two intergenic regions have promoting activities closely related to the sulfur nutritional status of the plants, since the expression levels of the GUS reporter gene were closely related to the thiol content in the tissues. RT-PCR analyses showed that the two genes flanking the intergenic regions (At1g12030 and GUS) were similarly induced under sulfur starvation. Discussion/ Conclusion The two intergenic regions could be useful to develop transgenic bioindicators, since they were able to promote reporter activation under different sulfur nutritional status. Moreover, transcriptional analysis suggests that these intergenic regions might have a bi-directional activity in controlling the expression of two flanking genes under sulfur limitation. New Arabidopsis lines carrying GUS reporter gene under the control of different portions of the intergenic region between At1g12030 and At1g12040 in the two possible orientations have been obtained. Such new lines will be characterized for the activity of the different synthetic promoters in response to plant sulfur nutritional status and/or sulfate availability in the soil solution.