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Article|25 Aug 2022|OPEN
The SlHB8 acts as a negative regulator in tapetum development and pollen wall formation in Tomato
Caiyu Wu1 ,† , Yang Yang1 ,† , Deding Su2,3 ,† , Canye Yu1 , Zhiqiang Xian2,3 , Zanlin Pan1 , Hongling Guan1 , Guojian Hu4 , Da Chen1 and Zhengguo Li2 , , Riyuan Chen1 , , Yanwei Hao,1 ,
1Key Laboratory of Horticultural Crop Biology and Germplasm Innovation in South China, Ministry of Agriculture, College of Horticulture, South China Agricultural University, Guangzhou 510642, China
2Key Laboratory of Plant Hormones and Development Regulation of Chongqing, School of Life Sciences, Chongqing University, Chongqing, China
3Center of Plant Functional Genomics, Institute of Advanced Interdisciplinary Studies, Chongqing University, Chongqing 400044, China
4UMR990 INRA/INP-ENSAT, Université de Toulouse, Castanet-Tolosan, France
*Corresponding author. E-mail: zhengguoli@cqu.edu.cn,rychen@scau.edu.cn,yanweihao@scau.edu.cn
Caiyu Wu,Yang Yang and Deding Su contributed equally to the study.

Horticulture Research 9,
Article number: uhac185 (2022)
doi: https://doi.org/10.1093/hr/uhac185
Views: 94

Received: 05 May 2022
Accepted: 13 Aug 2022
Published online: 25 Aug 2022

Abstract

Pollen development is crucial for the fruit setting process of tomatoes, but the underlying regulatory mechanism remains to be elucidated. Here, we report the isolation of one HD-Zip III family transcription factor, SlHB8, whose expression levels decreased as pollen development progressed. SlHB8 knockout using CRISPR/Cas9 increased pollen activity, subsequently inducing fruit setting, whereas overexpression displayed opposite phenotypes. Overexpression lines under control of the 35 s and p2A11 promoters revealed that SlHB8 reduced pollen activity by affecting early pollen development. Transmission electron microscopy and TUNEL analyses showed that SlHB8 accelerated tapetum degradation, leading to collapsed and infertile pollen without an intine and an abnormal exine. RNA-seq analysis of tomato anthers at the tetrad stage showed that SlHB8 positively regulates SPL/NZZ expression and the tapetum programmed cell death conserved genetic pathway DYT1–TDF1–AMS–MYB80 as well as other genes related to tapetum and pollen wall development. In addition, DNA affinity purification sequencing, electrophoretic mobility shift assay, yeast one-hybrid assay and dual-luciferase assay revealed SlHB8 directly activated the expression of genes related to pollen wall development. The study findings demonstrate that SlHB8 is involved in tapetum development and degradation and plays an important role in anther development.