The Physiological And Molecular Mechanisms Of The Tolerance To Low Boron Stress In Arabidopsis Mutant LBT

Boron (B) is an essential micronutrient for high plant growth. B deficiency and excess are neither not benefit for plant growth and development, which become one of serious agricultural problems. With the development of B measure technology, cell and molecule biological technology and release of model plant Arabidopsis genome sequence, studying on the physiological and molecular mechanisms of B uptake and transport using Arabidopsis plays an important role in improving B nutrient associated traits by genetic approach. In this study, an Arabidopsis mutant LBT and its wide type Col-0were used to investigate their various responses to low B stress by isotope tracing method, microscopic observation based on paraffin section and gene expression analysis, in order to dissect the physiological and molecular mechanisms of tolerance to low B stress in mutant LBT. Main results are as follow:1. The physiological base of tolerance to low B stress in Arabidopsis mutant LBTThe biomass associated traits of LBT and Col-0under low B condition were investigated by hydroponic culture, and the concentration of B in different tissues was analyzed by10B isotope tracing method. It suggested that the fresh and dry weights of shoot and root of LBT were significantly higher than those of Col-0, the total B concentration in shoot, young leaf and root of LBT and the10B concentration in shoot and young leaves of LBT were apparently higher than those of Col-0. It indicated that LBT possesses stronger uptake and transport abilities than Col-0.2. Morphological characteristics of LBT under low B stressRoot system associated traits, shoot growth phenotype and cellular structure and stoma number in leaf of LBT and Col-0under low B condition were investigated by root scanning and microscopic observation based on paraffin section. It indicated that total root length, root tip number, root volume and root surface of LBT were significantly higher than those of Col-0, LBT had a better growth that Col-0, bigger cell, more wider intercellular space and higher stoma number in young leaf existed in LBT than Col-0. It implied that B was prior transported to young tissue in mutant LBT which may be associated with transpiration. 3. Gene expression analysis for Arabidopsis B uptake and transport related genes in LBTIn order to identify whether interactions between LBT gene and BOR1, BOR2, BOR3, BOR4, NIP5;1, NIP6;1, WRKY6, FFT played roles in the process of B uptake and transport, gene expression analysis of the eight genes in LBT and Col-0under different B conditions was conducted by quantitative RT-PCR. It suggested that NIP5;1showed stronger expression in root of LBT than that of Col-0. Combining with the difference of B uptake between LBT and Col-0, we can speculate that stronger expression of NIPS;1in root conferred better B uptake ability in LBT, it implied that LBT gene may be associated with NIP5;1.In a word, Arabidopsis mutant LBT hold stronger growth advantages in response to low B stress at both shoot and root, and LBT has a stronger B uptake ability than Col-0, likely based on the stronger expression of NIP5;1in root induced by B limitation. Absorbed B by LBT is prior transported to young tissues for utilization.