Floral nectar of the obligate outcrossing Canavalia gladiata (Jacq.) DC. (Fabaceae) contains only one predominant protein, a class III acidic chitinase

X L Ma, Richard Milne, Hong-xia Zhou, Jiang-Yu Fang, Hong-Guang Zha

Research output: Contribution to journalArticle

Abstract / Description of output

Floral nectar can affect the fitness of insect-pollinated plants, through both attraction and manipulation of pollinators. Self-incompatible insect-pollinated plants receive more insect visits than their self-compatible relatives, and the nectar of such species might face more risk to be infested by the pathogens carried by pollinators than self-compatible plants. Proteins in nectar (nectarins) play an important role in the protection of nectar, but little is known regarding nectarins in self-incompatible species.

The nectarins from a self-incompatible and insect-pollinated leguminous crop, Canavalia gladiata, were separated using two-dimensional electrophoresis and analysed using mass spectrometry. The predominant nectarin gene was cloned and the gene expression pattern was investigated by quantitative real-time PCR. Chitinolytic activity in the nectar was tested with different substrates.

The C. gladiata nectar proteome only has one predominant nectarin, an acidic class III chitinases (CaChi3). The full-length CaChi3 gene was cloned, coding for a protein of 298 amino acids with a predicted signal peptide. CaChi3 has high similarity to members of the class III chitinase group, whose evolution has been dominated by purifying selection. CaChi3 was expressed in both nectary and leaves. CaChi3 showed thermostable chitinolytic activity by glycol-chitin zymography or using fluorogenic substrate but no lysozyme activity.

Chitinase might be a critical kind of proteinaceous component in nectar. The extremely simple nectar proteome in C. gladiata disproves a hypothesis that self-incompatible species always have more complex nectar proteomes. The accessibility of nectar might be a significant determinant of the evolutionary pressure to develop nectar defense mechanisms.
Original languageEnglish
Pages (from-to)749-759
Number of pages11
JournalPlant Biology
Issue number5
Publication statusPublished - 26 Jun 2017

Keywords / Materials (for Non-textual outputs)

  • Acidic class III chitinase
  • Canavalia gladiata
  • Floral nectar
  • Nectarin
  • Self-incompatibility


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