Proteomics and post-secretory content adjustment of Nicotiana tabacum nectar

Xue-Long Ma, Richard Milne, Hong-xia Zhou, Yue-Qin Song, Jiang-Yu Fang, Hong-Guang Zha

Research output: Contribution to journalArticlepeer-review

Abstract

Main conclusion
The tobacco nectar proteome mainly consists of pathogenesis-related proteins with two glycoproteins. Expression of nectarins was nonsynchronous, and not nectary specific. After secretion, tobacco nectar changed from sucrose-rich to hexose-rich.

Floral nectar proteins (nectarins) play important roles in inhibiting microbial growth in nectar, and probably also tailoring nectar chemistry before or after secretion; however very few plant species have had their nectar proteomes thoroughly investigated. Nectarins from Nicotiana tabacum (NT) were separated using two-dimensional gel electrophoresis, and then analyzed using mass spectrometry. Seven nectarins were identified: acidic endochitinase, β-xylosidase, α-galactosidase, α-amylase, G-type lectin S-receptor-like serine/threonine-protein kinase, pathogenesis-related protein 5, and early nodulin-like protein 2. An eighth nectarin, a glycoprotein with unknown function, was identified following isolation from NT nectar using a Qproteome total glycoprotein kit, separation by SDS-PAGE, and identification by mass spectrometry. Expression of all identified nectarins, plus four invertase genes, were analysed by qRT PCR; none of these genes had nectary-specific expression, and none had synchronous expression. The total content of sucrose, hexoses, proteins, phenolics and hydrogen peroxide were determined at different time intervals in secreted nectar, both within the nectar tube (in vivo) and following extraction from it during incubation at 30 °C for up to 40 h in plastic tubes (in vitro). After secretion, the ratio of hexose to sucrose substantially increased for in vivo nectar, but no sugar composition changes were detected in vitro. This implies that sucrose hydrolysis in vivo might be done by fixed apoplastic invertase. In addition, both protein and hydrogen peroxide levels declined in vitro but not in vivo, implying that some factors other than nectarins act to maintain their levels in the flower, after secretion.
Original languageEnglish
Pages (from-to)1703-1715
JournalPlanta
Volume250
Early online date14 Aug 2019
DOIs
Publication statusE-pub ahead of print - 14 Aug 2019

Keywords

  • floral nectar
  • gene expression pattern
  • glycoprotein
  • invertase
  • nectarin
  • post-secretory adjustment
  • tobacco

Fingerprint

Dive into the research topics of 'Proteomics and post-secretory content adjustment of Nicotiana tabacum nectar'. Together they form a unique fingerprint.

Cite this