Homologues of the Arabidopsis thaliana SHI/STY/LRP1 genes control auxin biosynthesis and affect growth and development in the moss Physcomitrella patens.
The plant hormone auxin plays fundamental roles in vascular plants. Although exogenous auxin also stimulates developmental transitions and growth in non-vascular plants, the effects of manipulating endogenous auxin levels have thus far not been reported. Here, we have altered the levels and sites of auxin production and accumulation in the moss Physcomitrella patens by changing the expression level of homologues of the Arabidopsis SHI/STY family proteins, which are positive regulators of auxin biosynthesis genes. Constitutive expression of PpSHI1 resulted in elevated auxin levels, increased and ectopic expression of the auxin response reporter GmGH3pro:GUS, and in an increased caulonema/chloronema ratio, an effect also induced by exogenous auxin application. In addition, we observed premature ageing and necrosis in cells ectopically expressing PpSHI1. Knockout of either of the two PpSHI genes resulted in reduced auxin levels and auxin biosynthesis rates in leafy shoots, reduced internode elongation, delayed ageing, a decreased caulonema/chloronema ratio and an increased number of axillary hairs, which constitute potential auxin biosynthesis sites. Some of the identified auxin functions appear to be analogous in vascular and non-vascular plants. Furthermore, the spatiotemporal expression of the PpSHI genes and GmGH3pro:GUS strongly overlap, suggesting that local auxin biosynthesis is important for the regulation of auxin peak formation in non-vascular plants.
Department of Plant Biology and Forest Genetics, Uppsala BioCenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
D Magnus
DM
Eklund
Mattias
M
Thelander
Katarina
K
Landberg
Veronika
V
Ståldal
Anders
A
Nilsson
Monika
M
Johansson
Isabel
I
Valsecchi
Eric R A
ER
Pederson
Mariusz
M
Kowalczyk
Karin
K
Ljung
Hans
H
Ronne
Eva
E
Sundberg
D017360:Arabidopsis / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development; D015139:Blotting, Southern; D044002:Bryophyta / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D005784:Gene Amplification; D055786:Gene Knockout Techniques; D018745:Genome, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D010641:Phenotype; D010937:Plant Growth Regulators / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods
D018744:DNA, Plant; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D003577:Cytochrome P-450 Enzyme System