Myosin XI is essential for tip growth in Physcomitrella patens.
Class XI myosins are plant specific and responsible for cytoplasmic streaming. Because of the large number of myosin XI genes in angiosperms, it has been difficult to determine their precise role, particularly with respect to tip growth. The moss Physcomitrella patens provides an ideal system to study myosin XI function. P. patens has only two myosin XI genes, and these genes encode proteins that are 94% identical to each other. To determine their role in tip growth, we used RNA interference to specifically silence each myosin XI gene using 5' untranslated region sequences. We discovered that the two myosin XI genes are functionally redundant, since silencing of either gene does not affect growth or polarity. However, simultaneous silencing of both myosin XIs results in severely stunted plants composed of small rounded cells. Although similar to the phenotype resulting from silencing of other actin-associated proteins, we show that this phenotype is not due to altered actin dynamics. Consistent with a role in tip growth, we show that a functional, full-length fusion of monomeric enhanced green fluorescent protein (mEGFP) to myosin XI accumulates at a subcortical, apical region of actively growing protonemal cells.
Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA. lvidali@wpi.edu
Luis
L
Vidali
Graham M
GM
Burkart
Robert C
RC
Augustine
Erin
E
Kerdavid
Erkan
E
Tüzel
Magdalena
M
Bezanilla
D020121:5' Untranslated Regions; D000199:Actins / Q000378:metabolism; D019068:Bryopsida / Q000235:genetics* / Q000254:growth & development; D018076:DNA, Complementary / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009218:Myosins / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development*; D034622:RNA Interference; D018749:RNA, Plant / Q000235:genetics
D020121:5' Untranslated Regions; D000199:Actins; D018076:DNA, Complementary; D010940:Plant Proteins; D018749:RNA, Plant; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D009218:Myosins