Biophysics / Internet Invited Lecture
OPTICAL FLUORESCENCE BIOSENSOR FOR PLANT WATER STRESS DETECTION
J-P.C.Chong, Singapore Polytechnic, Singapore
O. W. Liew, Singapore Polytechnic, Singapore
B.Q. Li, Nanyang Technological University, Singapore
A.K. Asundi, Nanyang Technological University, Singapore
Read on-line
DiscussionABSTRACT
Precision farming in arable agriculture and horticulture allows conservative use of resources that are applied according to plant needs. The growing concern for sustainability in crop production has accentuated the significance of our work to develop a rapid, sensitive and nondestructive method for real-time monitoring of plant stress under open field conditions. Elucidation of crop water status before the onset of irreversible cellular damage is critical for effective water management to ensure maximum crop yield and profit margin. We envisage that our ‘smart sensor’ can be linked to on-line feedback control of irrigation systems for ‘needs-based’ application of water in field crop production.
A two-component biosensing system comprising transgenic ‘Indicator Plants’ and a fibre optic fluorescence analyzer was developed to detect early signs of water stress in field crops before the permanent wilting point is reached. Our ‘Indicator Plants’ are transgenic Petunia hybrida harboring an Arabidopsis thaliana drought-responsive promoter linked to the enhanced green fluorescent protein (EGFP) coding sequence. Green fluorescence emitted by these ‘Indicator Plants’ in response to water stress are detected by our prototype optical fluorescence analyzer. The temporal and spatial pattern of water stress-induced EGFP expression were analyzed at the transcriptional and translational level by RT-PCR and fluorescence emission imaging, respectively. The shoot terminus of the ‘Indicator Plant’ was monitored under a fluorescence stereoscope at 0h, 1h, 2h, 4h, 6h, 8h, 10h and 24h time points following the onset of water stress. The intensity of the EGFP emission signal was also monitored spectroscopically.
No EGFP fluorescence was detected prior to induction of dehydration stress and emission intensity increased with increasing dehydration period, peaking at the 24h time point and found mainly in the stems, leaf veins and leaf tips. In contrast, basal levels of EGFP mRNA transcripts were observed at the 0h time point, gradually increasing from the 1h to the 2h time points. The amount of EGFP mRNA declined to barely observable levels at the 24 h time point. We also observed that the EGFP emission peak was 527 nm instead of the expected 509 nm, possibly due to skewing of the spectrum by endogenous autofluorescence of plant components like lignin. While fluorescence emission above endogenous background was detectable after 2 hours of water-stress treatment, the plants reached the permanent wilting point after 6 hours, showing that our system was able to detect water stress prior to plant entry into the stage of irreversible damage. Future work will be geared towards overcoming biological and instrument-related difficulties encountered in our initial prototype system. Further optimization to correlate the EGFP emission signals obtained by the spectroscopic analyzer with fluorescence stereoscope images is underway.
Representing Author:
Q. W. Liew, Singapore Polytechnic, (, Singapore)
This page was accessed 385 times.
Print
Add to your plan