Light Contributes To Salt Resistance Via GAI Protein Regulation In Arabidopsis Thaliana

As sessile organisms, plants modulate growth and development to adapt changeable environments. Previous studies reported that the DELLA proteins contribute to plant growth, development, and survival under salt stress. Recent reports that DELLA proteins were found to inhibit the hypocotyl elongation, which supports that DELLA proteins are involved in seedling photomorphogenesis. Moreover, inhibition of plant growth is beneficial for plant survival under adverse environments. It shows that plants integrate light signals with stress environments for adaptation and survival under stress. Although previous experimental data prove that light induced DELLA accumulation modulates plant growth, whereas and salt induced DELLA protein accumulation helps plant survival under stress. This study undertaken to know whether light enhances plant salt resistance, and also whether light helps plant salt resistance via DELLA?To find out the connection between light, salt stress and DELLA accumulation we used150mM NaCl and control treatment, to compare ht effect of low and high light on plant growth, development, and survival rate. We also performed immunoblot for DELLA accumulation at the seed germination and seedling stage, using endogenous GAI antibody. Additionally, we compared transcription level of selected slat-responsive genes in wild-type, gain-and loss-of-function DELLA mutants in response to light and salt treatments.The main findings of the present study can be summarized as follows:High light inhibits DELLA protein accumulation to promote seed germination under slat stress: This study indicates that light suppresses DELLA accumulation under slat (150mM NaCl) stress. We compared effect of light intensity to study the seed germination frequency. Results showed that high light inhibit DELLA accumulation to promote seed germination under salt stress.High light increases seedlings DELLA accumulation to promote salt resistance:Results showed significant increase in the number of lateral roots in high light grown seedlings as compared to seedlings grown in low light. Immunoblot results of also revealed that DELLA protein accumulations were promoted at the seedling stage.Light still promotes salt resistance in DELLA mutants:High light promotes obvious increase in the frequency of seed germination and number of lateral roots in wild-type and gain-and loss-of-function mutants. The results suggest that DELLA protein is not necessary for seed germination and root development, but the positive effect of high light on seed germination and lateral root growth in gai (GOF) seedlings is quite prominent. Additionally, high light increased seedling survival rate in all the lines under slat stress, although death rate was significantly higher in loss-of-function mutant as compared to wild-type and gain-of-function mutant. It indicates the pivotal role played by DELLA proteins for plant survival under salt stress.Light promotes transcriptional abundance of salt-responsive genes:As compared to low light high light increased the abundance of salt-responsive genes. The transcription level of salt-responsive genes in DELLA gain-of-function or loss-of-function was higher or lower respectively than in wild-type.Overall, light is not only the source of energy for plants but also provides information to help plant survival under stress via DELLA protein regulations.