Phenotype Analysis And Gene Cloning Of Root Architecture Mutant Raa3Induced By ABA In Arabidopsis

As a vital part of the plant, root system plays a role in these aspects of absorbing nutrients and water,transferring material, feeling the changes of soil environment and maintaining microorganisms. Meanwhile,the fixation and support of plants must also rely on a strong root system. So the root system is regarded asone of the organs of plants to absorb external substances which has an important impact on growth anddevelopment of plant. Lateral roots, as an important component of the root system, the development ofthem has direct influences for plant growth.The mutant material of this task based on seeds of Arabidopsis （Col-0） seeds were screened after EMSmutagenesis.. Compared with WT （wild-type）, the mutant presents a significant difference on root whenscreened by ABA, so named raa3（root architecture in response to ABA）. Lateral root number of mutantraa3is significantly less than WT after treated by10μM ABA treatment, and the phenotype can not berestored by exogenous auxin, suggesting that ABA may affect auxin transport of raa3. Further studies ofphenotypes of raa3show that the mutant raa3grows slower, has smaller body, bolts lower and boltsabout10days later than wild-type, at the same time, raa3flowers later. Stress analysis demonstrate thatraa3is more sensitive to H₂O₂than WT. There is no significant difference between raa3and WT undernormal conditions but the primary roots both of raa3and WT are severely inhibited after treated withdifferent concentration of H₂O₂, almost can’t grow any longer. The lateral roots of raa3are severelyinhibited and the number of LR of raa3is significantly less than that of WT, implying that H₂O₂may beinvolved in the ABA-regulated signaling pathway in Arabidopsis lateral root development. Statistics of thenumber of each stage of lateral root primordia development indicate that ABA mainly affects the earlystages of lateral root primordia. There are also significant differences in water loss, leaf surface temperatureand stomatal aperture between raa3and WT. Genetic analysis showed that raa3is single recessive genemutation. To apply the forward genetics method, we located this mutant gene on BAC T2O4of the top ofArabidopsis chromosome Ⅲ based on positional cloning.These studies have shown that ABA directly participated in the root architecture of Arabidopsis,which hinted that H₂O₂may be involved in the regulatory process of Arabidopsis lateral root by ABA. The identification and further functional analysis of raa3will help us to understand the molecular mechanism ofthe occurrence and development of lateral roots regulated by ABA.