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Front. Plant Sci. | doi: 10.3389/fpls.2019.00541

Cell wall invertase 3 affects cassava productivity via regulating sugar allocation from source to sink

 Wei Yan1, 2, 3,  Xiaoyun Wu2, 4, Yanan Li3, Guanghua Liu3, Tailing Jiang3, Zhanfei Cui2, 4,  Qiuxiang Ma2, Lijuan Luo1* and  Peng Zhang2, 4*
  • 1Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, Hainan University, China
  • 2Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences (CAS), China
  • 3Institute of Tropical and Subtropical Crops, Yunnan Academy of Agricultural Sciences, China
  • 4University of Chinese Academy of Sciences (UCAS), China

Storage roots are the main sink for photo-assimilate accumulation and reflect cassava yield and productivity. Regulation of sugar partitioning from leaves to storage roots has not been elucidated. Cell wall invertases are involved in the hydrolysis of sugar during phloem unloading of vascular plants to control plant development and sink strength but have rarely been studied in root crops like cassava. MeCWINV3 encodes a typical cell wall invertase in cassava and is mainly expressed in vascular bundles. The gene is highly expressed in leaves, especially mature leaves, in response to diurnal rhythm. When MeCWINV3 was overexpressed in cassava, sugar export from leaves to storage roots was largely inhibited and sucrose hydrolysis in leaves was accelerated, leading to increased transient starch accumulation by blocking starch degradation and reduced overall plant growth. The progress of leaf senescence was promoted in the MeCWINV3 over-expressed cassava plants with increased expression of senescence-related genes. Storage root development was also delayed because of dramatically reduced sugar allocation from leaves. As a result, the transcriptional expression of starch biosynthetic genes such as small subunit ADP-glucose pyrophosphorylase, granule‐bound starch synthase I, and starch branching enzyme I was reduced in accordance with insufficient sugar supply in the storage roots of the transgenic plants. These results show that MeCWINV3 regulates sugar allocation from source to sink and maintains sugar balance in cassava, thus affecting yield of cassava storage roots.

Keywords: cassava, cell wall invertase, phleom loading, sugar allocation, Storage root, productivity

Received: 29 Dec 2018; Accepted: 09 Apr 2019.

Edited by:

Wim Van Den Ende, KU Leuven, Belgium

Reviewed by:

Annette Morvan-Bertrand, University of Caen Normandy, France
Hamada AbdElgawad, Faculty of Science, Beni-Suef University, Egypt  

Copyright: © 2019 Yan, Wu, Li, Liu, Jiang, Cui, Ma, Luo and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Prof. Lijuan Luo, Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, Hainan University, Haikou, Hainan Province, China, 990908@hainu.edu.cn
Prof. Peng Zhang, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences (CAS), Shanghai, China, zhangpeng@sibs.ac.cn