Effects Of Soil Water Stress On Bt Protein Expression And Nitrogen Metabolism In Bt Cotton

To clarify soil moisture stress effects on insect resistance of Bt transgenic cotton (Bt cotton), conventional cultivar Sikangl and hybrid cultivar Sikang3 were used as tested materials, during 2014-2015 cotton growth season at Key laboratory of Genetics and Physiology, Yangzhou University. The potted cotton samples at squaring stage and boll stage designed to different water deficit (soil water capacity of 15% 30%,45% and 60% of the maximum water capacity), water logging in different level (soil water capacity of 90%,100% and 2cm waterlogging of the maximum water capacity) soil water capacity 60% and 90% continued stress for 24h,48h,72h, 96h and 120h to test Bt insecticidal protein expression and correlation in physiological mechanisms of nitrogen metabolism. The results were as follows:l.In comparison to the control (CK,soil moisture content 75%), Bt protein content had greater degree of decline at both bud stage and boll stage with the increase of soil moisture deficit level. Two cultivars have shown a decline to 60% in the soil water capacity, and the decline of square and boll Bt protein has reached a significant level. At Soil water capacity of 60%,45%,30% and 15% after 96h water deficit Stress, cultivar Sikangl bud Bt protein content decreased by 42.03%,46.55%,50.00%,57.16%, boll shell Bt protein content decreased by 17.71%、23.61%、36.04%、55.57%, respectively, Bt protein content of Sikang3 bud decreased by 23.95%,62.32%,68.68%,72.84%, boll shell decreased by 27.82%,43.78%,68.15%,70.69%; With waterlogging degree increase of soil moisture, Bt protein content in square stage and boll stage has same degree of decline. Two cultivars have showed in the soil water capacity increased to 90%, the square Bt insecticidal protein content decline significantly. At Soil water capacity were 90%,100%, waterlogging 2cm after 96h, the square Bt insecticidal protein of Sikangl decreased by 36.52%,42.08%,51.40%, boll shell insecticidal protein decreased by 10.30%, 18.33%,32.81% respectively; the square Bt insecticidal protein content of Sikang3 decreased by 19.18%,57.19%,64.48%, boll shell insecticidal protein decreased by 16.36%,39.13%,67.43% respectively. Similar characteristics was also observed for the fiber and seeds protein content, under the soil drought and waterlogging stress,2.Under soil water deficit (water capacity 60%) and waterlogging (water capacity 90%) sustained stress for 24-120h, the results showed that the square and boll Bt protein content decreased with prolonged stress under water deficit stress duration. The longer the stress, the greater the decline. Compared with the control (no stress), Bt protein content in square significantly decreased in stress to after 96h; boll significantly decreased in stress to after 72h. Stress continued to 120h, Square, boll shell, cotton seed and fiber Bt protein of SiKangl decreased by 35.33%,46.96%,33.03%,19.66% respectively, SiKang3 decreased by 44.81%, 45.49%,40.41%,29.66% respectively; The square and boll has same Bt protein content decreased with prolonged stress under the waterlodgging stress,, and stress the longer, the greater the decline. Compared with the control, Bt protein content decreased significantly for the square and boll when stressed to after 96h. Stress continued to 120h, square, boll shell, cotton seed and fiber Bt protein of Sikangl decreased by 33.97%,31.35%,44.67% and 19.66% respectively, Sikang3 decreased by 35.84%,27.42%,38.85% and 24.99% respectively, the two cultivars consistent performances.3.Under water deficit stress, the square Bt insecticidal protein expression decreased, while soluble protein content increased, amino acid content decreased, NR, GPT, GOT, GS, GOT activity decreased, protease and peptide activity increased; the boll soluble protein content decreased, amino acid content increased, NR, GPT, GOT, GS, GOT activity decreased, peptide and protease activity increased. The waterlogged stress showed declined Bt insecticidal protein expression of both square and boll while soluble protein content decreased, increased amino acid content, NR, GPT, GOT, GS, GOT activity decreased, peptide and protease activity increased. Correlation analysis showed that square Bt protein content was significantly negatively correlated with the soluble proteins contents, peptides and protease activity, significantly positive relationship with the free amino acids and NR, GOT, GPT, GS, GOGAT activity under water deficit adversity; The boll Bt protein content under soil water deficit stress, boll and square Bt protein content under waterlogged soil of adversity was a significant negative correlation with free amino acids, peptides and protease activities, significant positive correlation with soluble protein content, NR, GOT, GPT, GS and GOGAT activities.These results suggest that soil moisture stress can cause decrease of bud and boll insecticidal protein expression in Bt cotton, so the production should pay close attention to drought and waterlogging stress and degree of insect resistance to Bt cotton to prevent bollworm and other related harm pests.