Changes in spatiotemporal protein and amino acid gradients in wheat caryopsis after N-topdressing

• Published in: Plant science (Limerick) Vol. 291; p. 110336
• Main Authors: Zhong, Yingxin, Vidkjær, Nanna Hjort, Massange-Sanchez, Julio A., Laursen, Bente Birgitte, Gislum, René, Borg, Søren, Jiang, Dong, Hebelstrup, Kim Henrik
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01-02-2020
• Subjects: Amino acids; Gene expression profiling; Laser capture microdissection; Spatial distribution; Wheat caryopsis; Amino acids; Laser capture microdissection; Spatial distribution; Wheat caryopsis; Gene expression profiling
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2019.110336

•Delay of topdressing results in a higher content of free amino acids in wheat caryopsis.•A higher content of free amino acids gives a higher final grain nitrogen content.•The gradient of free amino acids change during caryopsis development.•Grain protein content is limit by amino acid supply rather than gene transcription.
Wheat grain nitrogen content displays large variations within different pearling fractions of grains because of radial gradients in the protein content. We identified how spatiotemporal mechanisms regulate this. The protein gradients emerged clearly at 19 days after anthesis, with the highest N content in aleurone and seed coat, followed by outer endosperm, whereas the lowest was in middle and inner endosperm. Laser microdissection, qRT-PCR and LC–MS were used to dissect tissue from aleurone, outer endosperm, middle endosperm, inner endosperm and transfer cells, measure gene expression and levels of free and protein-bound amino acids, respectively. The results showed that different FAA transportation pathways worked in parallel during grain filling stage while the grain protein gradient did not follow spatial expression of storage proteins. Additionally, two nitrogen (N) topdressing timings were conducted, either at the emergence of top third leaf (standard timing) or top first leaf (delayed timing), finding that delayed N topdressing enhanced both amino acids supply and protein synthesis capacity. The results provide insight into protein synthesis and amino acid transport pathways in endosperm and suggest targets for the enhancement of specialty pearled wheat with higher quality.