Auxin Homeostasis Regulation Transcription Factor URO Regulate Arabidopsis Gametophyte Development

Auxin is one of the most important plant hormone,the concentration of local free state auxin determines the function of auxin.There are three factors regulate the concentration of free state auxin in tissues and cells:auxin polar transport,auxin synthesis and auxin metabolism.Among them,the synthesis and polar transport of auxin has been studied detaily,acquired a lot of research results.Metabolism of auxin mainly includes the transformation between combination state auxin and free state auxin,includes the degradation of some combination state auxin.Currently,there are less progress in auxin metabolic regulation,only know some of the relevant enzymes which play a role.Whether this process has an important role in plant growth and development,as well as the regulation mechanism of this process,we know very little.Research of this part has become one of the weakest link in auxin study field,badly in need of development.Our laboratory reported URO gene is the first reported transcription factor which regulates the auxin homeostatic in plant.Existing research results show that in uro mutant,free auxin's content increased significantly because of the excessive expression of URO gene,then there is a series of phenotypes associatied with excess auxin.But further insight into the function and mechanism of URO gene required study its deletion mutant.We adopted the method of artificial miRNA and get the Arabidopsis URO gene loss of function mutant amiRNA URO.The expression of URO gene in amiRNA URO transformants is downregulated and the endogenous auxin content is decreased,these are further evidence of URO gene is a transcription factor which regulates the auxin metabolism.Our study shows that URO gene involved in the regulation of Arabidopsis reproductive development through interacting with the SPL gene.URO gene is also involved in vegetative growth,including stomatal and leaf development.We can not obtain the homozygotes of amiRNA URO,carefully observed the T1 generation plants,we found a series of phenotypes:dwarfing height,smaller leaf size,abnormal stomatal development,abnormal flower pattern,abnormal pollen development,shorter pods and declining fertility.Scanning electron microscopy examination showed that the pollen wall surface of transformants is abnormal,showing a smooth shape.Semi-thin resin sections examination showed that the tapetum formation in anthers is abnormal,some microspores are broken and the number of pollen is reduced.Genetic analysis showed that the gametes with amiRNA URO all died.qRT-RCR analysis showed that the expression of nuclear replication-related genes MCM2,MCM5 was changed in the transformants leaves.These indicate that URO gene involved in regulating cell genome replication and division.In addition,we have explored the relationship between URO gene and auxin synthesis related genes,further reveal the function of URO gene.