The Gene Of SMB Is Involved In The Regulation Of Root Tropism In Arabidopsis Thaliana

Drought and salt stress caused by drought and salinization are the main abiotic stresses that cause a sharp decline in global crop yields.Roots,as the most important nutrient-absorbing organs of plants,are particularly important for perception of the external environment When encountering unfavorable environmental factors,it can avoid and grow in a favorable direction,that is,the root direction(Tropic movement)。The root crown is the first to sense the external signal to protect the meristem,and the SMB gene can regulate the root The maturation of crown cells.This study found that the SMB gene mutant smb-3 lost its response to the apex of the root tip under stress.In order to explore the mechanism and role of SMB in the whole regulation of the apex of the root tip,this study did related experiments and achieved the following results.Under the condition of salt stress,the root tip of smb-3 did not appear to avoid salt stress growth(Halotropism).the root tip of smb-3 did not show salt avoidance.By weighing the fresh weight of smb-3 and Col-0 growing on salt-salt full salt plate and salt-stress bevel plate for several days,smb-3 was found did not cause the fresh weight loss to be greater than Col-0 because the root tip was immersed in the salt stress medium,and then by measuring the sodium and potassium elements of smb-3and Col-0 under salt stress,There are also instantaneous flow rates of salt ions in different areas of the root tip,and it was found that smb-3 had the same salt absorption as Col-0.However,the apical phenotypes of the root tips differ greatly.Through the transcription marker gene DR5::N7-Venus induced by auxin synthesis,it was found that there is a huge difference in the distribution of auxins in the root tips of smb-3and Col-0 under stress.Under salt stress,root auxin can be redistributed to regulate the growth direction of root tips.Subsequently,a vector was constructed to determine the location and expression of SMB under salt stress.It was found that salt stress did not change the expression and location of SMB gene.Under the conditions of simulating drought stress with sorbitol,the root tips of smb-3 also failed to show hydrotropism like Col-0.The same transcription marker gene DR5::N7-Venus induced by auxin synthesis found that under drought stress,the distribution of apical auxin in smb-3 and Col-0 had the same difference as that under salt stress.However,under the same gravitational stimulation,smb-3 and Col-0maintained the same geotropism,and the distribution of apical auxin also remained the same.In summary,under the salt stress,smb-3 were lack of salt avoidance that seems to have nothing to do with salt absorption capacity.The halotropism depends on the SMB function to mediate the asymmetric distribution of auxin.Under drought stress,the occurrence of hydrotropism also requires SMB to mediate the asymmetric distribution of auxin.