Evaluation Of The Drought Tolerance For Nitric Oxide-Related Mutants In Arabidopsis

Nitric oxide is a small gas molecule,It regulate many biological process in plants.When we try to research the roles of NO in plants drought tolerance,we find the stature size plans plays a very important role.It has been reported that Arabidopsis noal mutant, defective in nitric oxide (NO) production and with a small stature, is more resistant to water deficit than wilde-type Col-0. To investigate whether the size of noal plant plays a role in drought tolerance, Col-0, noal as well as gsnor1-3, a GSNOR1loss-of-function mutant, defective in de-nitrosylation and with an comparable stature to noal, were subjected to drought treatment either in separate containers or in the same containers. Our results showed that both noal and gsnorl-3plants survived longer than Col-0under drought conditions when grown in separate containers. noal was more tolerant to drought than gsnorl-3as it survived2-3days longer than gsnorl-3in the separate container experiment. However, when randomly grown in the same containers, the plants of the three genotypes dried out almost at the same time, indicating that the reduced transpirations due to the smaller sizes of the mutant plant might account for the prolonged surviving under drought in separate containers. In the same container experiment, the accelerated water loss caused by the transpiration of Col-0plants most likely contributed to the earlier dry-out of noal and gsnor1-3because certain amount of the transpired water through Col-0could have been used by noal or gsnor1-3if grown in separate-pots. Interestingly, noa1had less stomata densities and the stomatal closures of both noal and gsnor1-3were more sensitive to ABA. In addition, noal was more resistant to osmotic stress than both Col-0and gsnor1-3. While, the water loss rates of detached leaves of both noa1and gsnorl-3were greater than that of Col-0, suggesting that the water loss rates of detached leaves may not represent that of in planta leaves;RT-PCR results revealed that no significant differences were observed for the expression of genes related to drought resistance/tolerance Together, our results suggest that1) plant sizes of different genotypes must be taken into consideration in evaluating drought trait and multiple approaches and criteria are needed to ensure the accurate evaluation of drought tolerance/resistance;2) both the same-container and the separate-container experiments are necessary for screening the resistant genotypes or tolerant genotypes when the tested genotypes have big differences in statures; However, only the separate-container experiment is required when the tested genotypes have comparable statures;3) the increased drought tolerance of noal is resulted from combined effects of the smaller stature, the reduced stomatal density on the leaves, the increased sensitivity of stomata closure to ABA and the enhanced resistance to osmotic stress;4). water loss rate of detached leaves is not a good indicator in evaluating of drought tolerance;5) the drought tolerance displayed by noal is not resulted from higher expression of genes involved in drought tolerance.People do a lot of work on NO in plant growth and development of biological and abiotic stress.but little research on the role of NO in plant drought re si stance. Our experimental results not only have important theoretical value for people further understanding the main role of NO，but also give people some important guidance how-to choose materials and culture when evaluating drought tolerance.