The 5′-Untranslated Region of the ntp303 Gene Strongly Enhances Translation during Pollen Tube Growth, But Not during Pollen Maturation

Abstract

Transcripts of the ntp303 gene accumulate abundantly throughout pollen development, whereas the protein only accumulates to detectable levels after pollen germination. In an attempt to explain the divergence in the accumulation profiles of the mRNA and the protein, we investigated the role of the untranslated regions (UTRs) in enhancing ntp303 translation during the transition from developing to germinating pollen. Luciferase reporter gene fusion constructs containing the ntp3035′-UTR gave rise to luciferase activity that was up to 60-fold higher during pollen tube growth than that of constructs containing different 5′-UTRs. No apparent differences in the luciferase activity of these constructs were observed during pollen development. Thentp303 5′-UTR-mediated increase in luciferase activity was not significantly influenced by coding region or 3′-UTR sequences. Furthermore, enhanced luciferase activity directed by thentp303 5′-UTR occurred predominantly at the post-transcriptional level. A series of 5′-UTR deletion constructs was created to identify putative regulatory sequences required for the high level of translation during pollen tube growth. Two predicted stem loop structures (H-I and H-II) caused a complete inhibition of the enhanced translation after their total or partial deletion. A (GAA)8repeat within the H-I stem loop structure was demonstrated to be important for the modulation of translation efficiency. The H-II stem loop structure was found to be essential for the determination of mRNA stability.

The MADS Box Transcription Factor ZmMADS2 Is Required for Anther and Pollen Maturation in Maize and Accumulates in Apoptotic Bodies during Anther Dehiscence

“…This gene is expressed in sporophytic tissues of the anther, mature pollen, and root caps, but also in the endosperm (Twell et al, 1991) and was shown recently to be a ligand of the pollen receptor kinase LePRK2 (Tang et al, 2002). Translational enhancement of the late pollen genes LAT52 and NTP303 has been reported to be mediated by their 5Ј-UTRs (Bate et al, 1996;Hulzink et al, 2002). Transient transformation assays with ZmMADS2 promoter deletion constructs revealed only slight differences in expression levels of the luciferase reporter gene either with or without 5Ј-UTR, indicating that the functional role of the 5Ј-UTR of ZmMADS2 is different.…”

Brassica napus Rop GTPases and their expression in microspore cultures

“…In contrast, the RNA folding predictions for the BnRop9 and Rop3 upstream regions showed little secondary structure. Perhaps, the folding in the pollenspeciWc ROP mRNA allows it to survive storage in (Hulzink et al 2002). The presence and absence of uORFs in members of the highly related ROP gene family might provide an interesting model system to explore the roles of these elements in gene regulation.…”

Function and molecular evolution of multicopper blue proteins

“…Bp10 from Brassica napus (ASO_BRANA), expressed in developing pollen, shows 30% sequence identity to ascorbate oxidase, but the copper-binding residues are not conserved [74]. The NTP303 gene is related to pollen tube growth and is expressed abundantly during pollen development [75]. The SKU5 gene from Arabidopsis thaliana codes another protein homologous to ascorbate oxidase, but it has no copper-binding center [76].…”