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Plant function and evolutionary biology
RESEARCH ARTICLE (Open Access)

Concurrent overexpression of amino acid permease AAP1(3a) and SUT1 sucrose transporter in pea resulted in increased seed number and changed cytokinin and protein levels

Jan E. Grant https://orcid.org/0000-0002-6806-8226 A H , Annu Ninan B G , Natalia Cripps-Guazzone A F , Martin Shaw A , Jiancheng Song B C , Ivan Petřík E , Ondřej Novák E , Mechthild Tegeder D and Paula E. Jameson https://orcid.org/0000-0002-6371-8234 B H
+ Author Affiliations
- Author Affiliations

A The New Zealand Institute for Plant and Food Research Limited, Private Bag 4704, Christchurch 8140, New Zealand.

B School of Biological Sciences, University of Canterbury, Christchurch 8140, New Zealand.

C School of Life Sciences, Yantai University, Yantai 264005, China.

D School of Biological Sciences, Washington State University, Pullman, WA, USA.

E Laboratory of Growth Regulators, Faculty of Science, Palacký University, and Institute of Experimental Botany of the Czech Academy of Sciences, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic.

F Faculty of Agriculture and Life Sciences, Lincoln University, New Zealand.

G The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand.

H Corresponding authors. Emails: jan.grant@plantandfood.co.nz; paula.jameson@canterbury.ac.nz

Functional Plant Biology 48(9) 889-904 https://doi.org/10.1071/FP21011
Submitted: 12 January 2021  Accepted: 30 March 2021   Published: 25 May 2021

Journal Compilation © CSIRO 2021 Open Access CC BY-NC-ND

Abstract

Using pea as our model crop, we sought to understand the regulatory control over the import of sugars and amino acids into the developing seeds and its importance for seed yield and quality. Transgenic peas simultaneously overexpressing a sucrose transporter and an amino acid transporter were developed. Pod walls, seed coats, and cotyledons were analysed separately, as well as leaves subtending developing pods. Sucrose, starch, protein, free amino acids, and endogenous cytokinins were measured during development. Temporal gene expression analyses (RT-qPCR) of amino acid (AAP), sucrose (SUT), and SWEET transporter family members, and those from cell wall invertase, cytokinin biosynthetic (IPT) and degradation (CKX) gene families indicated a strong effect of the transgenes on gene expression. In seed coats of the double transgenics, increased content and prolonged presence of cytokinin was particularly noticeable. The transgenes effectively promoted transition of young sink leaves into source leaves. We suggest the increased flux of sucrose and amino acids from source to sink, along with increased interaction between cytokinin and cell wall invertase in developing seed coats led to enhanced sink activity, resulting in higher cotyledon sucrose at process pea harvest, and increased seed number and protein content at maturity.

Keywords: Pisum sativum, sucrose, legume, AAP, SUT, SWEET, cell wall invertase, IPT, CKX, transgenic, process peas, transgenics, seed coat, seed yield.


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