An ankyrin repeat-containing protein, characterized as a ubiquitin ligase, is closely associated with membrane-enclosed organelles and required for pollen germination and pollen tube growth in lily.
Exhibiting rapid polarized growth, the pollen tube delivers the male gametes into the ovule for fertilization in higher plants. To get an overall picture of gene expression during pollen germination and pollen tube growth, we profiled the transcription patterns of 1,536 pollen cDNAs from lily (Lilium longiflorum) by microarray. Among those that exhibited significant differential expression, a cDNA named lily ankyrin repeat-containing protein (LlANK) was thoroughly studied. The full-length LlANK cDNA sequence predicts a protein containing five tandem ankyrin repeats and a RING zinc-finger domain. The LlANK protein possesses ubiquitin ligase activity in vitro. RNA blots demonstrated that LlANK transcript is present in mature pollen and its level, interestingly contrary to most pollen mRNAs, up-regulated significantly during pollen germination and pollen tube growth. When fused with green fluorescent protein and transiently expressed in pollen, LlANK was found dominantly associated with membrane-enclosed organelles as well as the generative cell. Overexpression of LlANK, however, led to abnormal growth of the pollen tube. On the other hand, transient silencing of LlANK impaired pollen germination and tube growth. Taken together, these results showed that LlANK is a ubiquitin ligase associated with membrane-enclosed organelles and required for polarized pollen tube growth.
Huang
Jian
J
Protein Science Laboratory of the Ministry of Education, Department of Biological Sciences and Biotechnologies, Tsinghua University, Beijing 100084, China.
Chen
Feng
F
Del Casino
Cecilia
C
Autino
Antonella
A
Shen
Mouhua
M
Yuan
Shuai
S
Peng
Jia
J
Shi
Hexin
H
Wang
Chen
C
Cresti
Mauro
M
Li
Yiqin
Y
D017089:Ankyrin Repeat; D020869:Gene Expression Profiling; D020868:Gene Silencing; D049452:Green Fluorescent Proteins / Q000032:analysis; D007425:Intracellular Membranes / Q000201:enzymology; D027762:Lilium / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D015388:Organelles / Q000201:enzymology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011058:Pollen / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development*; D011993:Recombinant Fusion Proteins / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D015854:Up-Regulation; D016335:Zinc Fingers
D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D025801:Ubiquitin; D049452:Green Fluorescent Proteins; D044767:Ubiquitin-Protein Ligases