Auxin On Anther And Plant Vascular Development Role

It was well known that auxin is critical for the anther/pollen grain development,however, the clear distribution and detailed effects of auxin are still unclear. We heredescribed, through analyzing GUS activities of Arabidopsis lines harbouring auxinresponse elements DR5-GUS, that auxin was accumulated in the anther mainlyfocused on tapetum and pollen grains and weak in other tissue cell during flowerstage 10-12 and sepal from flower stage 12-15. Further studies employing theindoleacetic-acid-lysine synthetase(iaaL) coding gene from Pseudomonas syringaesubsp. savastanoi under control of an Arabidopsis promoter, of Arabidopsisphosphatidylinositol monophosphate 5-kinase (AtPIP5K1), with flowerfilament-specific expression showed that block of auxin flow of filaments resulted inshortened filaments and more interestingly, defected pollen grains. Similarphenotype was observed in tobacco plants transformed with same construct,confirming the effects of auxin flow in filaments on anther development. Detailedstudies further showed that the meiosis process of pollen grain was normal while themitosis at later stage was significantly defected, revealing the effects of auxin flowin filaments on mitosis process of pollen grain. Analysis employing [¹⁴C]IAA, aswell the expression of AtPIN1, coding for auxin efflux carrier, demonstrated thepresence of polar auxin transport in filaments.By the way, AtPIP5K1 gene was also expressed in vascular bundle of root andlateral root, as well as procabium of stem cell. Application the same strategy, wewant to know what effect it would give rise to on vascular development whendecreased the auxin content in AtPIP5K1 expression site of root and stem.Experiments results showed that transgenic plant was short and deduced apicaldominance. Their root was distinctly shortened and the number of lateral root wasdecreased in shoot growth phase. Deficiency auxin content in procambia wouldchange the capacity of division and differentiation and the cell number of differentform of procabium at different development stage was less than the normal. It wasconfined the stem circle to widen further and thus led to irregular shape stem. Thepaper gave the reasonable explanation on the auxin effects on vascular developmentwhich was not reported before, although shallow analysis.