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Front. Plant Sci. | doi: 10.3389/fpls.2018.01856

Overexpression of PpSnRK1α in tomato promotes fruit ripening by enhancing RIPENING INHIBITOR regulation pathway.

 Wen Yu1, 2, 3, Fu T. Peng1, 2, 3*, Gui F. Wang4, Jing J. Luo1 and  Yuan S. Xiao1*
  • 1Shandong Agricultural University, China
  • 2College of Horticulture Science and Engineering, Shandong Agricultural University, China
  • 3State Key Laboratory of Crop Biology, Shandong Agricultural University, China
  • 4Shandong Institute of Pomology, China

As a conserved kinase complex, sucrose non-fermenting-1-related protein kinase 1 (SnRK1) is a major regulator of plant growth and development. In our previous study, overexpression of MhSnRK1 in tomato (Solanum lycopersicum L.) modified fruit maturation: the transgenic fruit ripened earlier than the wild type. However, the mechanism by which fruit maturation is regulated by SnRK1 is not clear; therefore, the test materials used were the transgenic tomato lines (OE-1, OE-3, and OE-4) overexpressing the coding gene of peach (Prunus persica (L.) Batsch) SNF1-related kinase α subunit (PpSnRK1α). The activity of SnRK1 kinase in transgenic tomato lines OE-1, OE-3, and OE-4 was higher than that in the wild type at different periods of fruit development; in the pink coloring period the SnRK1 kinase activity increased the most, with 23.5%, 28.8%, and 21.4% increases, respectively. The content of starch and soluble sugars in red ripe transgenic fruit significantly increased, while the soluble protein and titratable acid content decreased significantly. We also found that the tomatoes overexpressing PpSnRK1α matured approximately 10 days earlier than the wild type. Moreover, the yeast-two-hybrid assay showed that PpSnRK1α interacted with the MADS-box transcription factor SIRIN, which acts as an essential regulator of tomato fruit ripening. The BiFC technology further validated the location of the PpSnRK1α interaction sites within the nucleus. The quantitative real-time PCR analysis showed that RIN expression was up-regulated by PpSnRK1α overexpression; the expression of RIN-targeted transcription factor genes NOR and FUL1 increased during different stages of fruit development. The expression of key genes, ACS2, ACS4, and E8, in ethylene synthesis also changed accordingly, and the ethylene emitted by the red ripe fruit increased by 36.1% to 43.9% compared with the wild type. These results suggest that PpSnRK1α interacts with SIRIN, increasing the expression of RIN, thereby regulating the expression of downstream ripening-related genes, finally promoting fruit ripening.

Keywords: SnRK1 protein kinase, RIN, Fruit ripening, peach, Tomato

Received: 28 Jul 2018; Accepted: 30 Nov 2018.

Edited by:

Francisco J. Corpas, Spanish National Research Council (CSIC), Spain

Reviewed by:

Rogerio R. Sotelo-Mundo, Centro de Investigación en Alimentación y Desarrollo (CIAD), Mexico
Avtar K. Handa, Purdue University, United States  

Copyright: © 2018 Yu, Peng, Wang, Luo and Xiao. 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. Fu T. Peng, Shandong Agricultural University, Tai'an, China, pft@sdau.edu.cn
Dr. Yuan S. Xiao, Shandong Agricultural University, Tai'an, China, yuansongx2013@163.com