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Article|07 Mar 2022|OPEN
Cytokinins are involved in regulation of tomato pericarp thickness and fruit size
Lijun Gan1 , , Mengying Song1 , Xuechun Wang1 , Na Yang1 , Hu Li2 , Xuexia Liu1 and Yi Li,3,4 ,
1College of Life Sciences, Nanjing Agricultural University, No. 1 Weigang, Nanjing 210095, China
2State Key Laboratory of Crop Genetics and Germplasm Enhancement and the College of Horticulture, Nanjing Agricultural University, No. 1 Weigang, Nanjing 210095, China
3Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT 06269, USA
4Yi Li holds a no-pay visiting professor position at Nanjing Agricultural University
*Corresponding author. E-mail: ganlj@njau.edu.cn,yi.li@uconn.edu

Horticulture Research 9,
Article number: uhab041 (2022)
doi: https://doi.org/10.1093/hr/uhab041
Views: 371

Received: 08 Jun 2021
Accepted: 23 Oct 2021
Published online: 07 Mar 2022

Abstract

Although cytokinins (CKs) regulate fruit development, no direct genetic evidence supports the role of endogenous CKs in pericarp growth or development or fruit size. Here, we report that the reduction in levels of endogenous active CKs via overexpression of the CK-inactivating enzyme gene AtCKX2 specifically in fruit tissues resulted in reduced pericarp thickness and smaller fruit size compared with wild-type control fruits. Pericarp thickness and single fruit weight in transgenic plants were significantly reduced. Analysis of paraffin sections showed that the reduced pericarp thickness was due largely to a decreased number of cells, and thus decreased cell division. Transcriptome profiling showed that the expression of cell division- and expansion-related genes was reduced in AtCKX2-overexpressing fruits. In addition, the expression of auxin-signaling and gibberellin-biosynthetic genes was repressed, whereas that of gibberellin-inactivating genes was enhanced, in AtCKX2-overexpressing fruits. These results demonstrate that endogenous CKs regulate pericarp cell division and subsequently fruit size. They also suggest that CKs interact with auxin and gibberellins in regulating tomato pericarp thickness and fruit size.