Effects of the sliaa9 Mutation on Shoot Elongation Growth of Tomato Cultivars.

Chihiro Abe-Hara,Risa Ueta,Kohji Yamada,Yuriko Osakabe,Naoki Wada,Keishi Osakabe,Ryosuke Hashimoto

doi:10.3389/fpls.2021.627832

Chihiro Abe-Hara, Risa Ueta + Show 5 more

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https://doi.org/10.3389/fpls.2021.627832

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Abstract

Tomato INDOLE-3-ACETIC ACID9 (SlIAA9) is a transcriptional repressor in auxin signal transduction, and SlIAA9 knockout tomato plants develop parthenocarpic fruits without fertilization. We generated sliaa9 mutants with parthenocarpy in several commercial tomato cultivars (Moneymaker, Rio Grande, and Ailsa Craig) using CRISPR-Cas9, and null-segregant lines in the T1 generation were isolated by self-pollination, which was confirmed by PCR and Southern blot analysis. We then estimated shoot growth phenotypes of the mutant plants under different light (low and normal) conditions. The shoot length of sliaa9 plants in Moneymaker and Rio Grande was smaller than those of wild-type cultivars in low light conditions, whereas there was not clear difference between the mutant of Ailsa Craig and the wild-type under both light conditions. Furthermore, young seedlings in Rio Grande exhibited shade avoidance response in hypocotyl growth, in which the hypocotyl lengths were increased in low light conditions, and sliaa9 mutant seedlings of Ailsa Craig exhibited enhanced responses in this phenotype. Fruit production and growth rates were similar among the sliaa9 mutant tomato cultivars. These results suggest that control mechanisms involved in the interaction of AUX/IAA9 and lights condition in elongation growth differ among commercial tomato cultivars.

Highlights

Tomato (Solanum lycopersicum) – a model horticultural crop – is one of the most important vegetable and fruit crops worldwide
We have previously reported the generation of sliaa9 knockout mutants using the clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein-9 nuclease (Cas9) system; the sliaa9 mutant showed altered leaf morphology and parthenocarpy (Ueta et al, 2017)
Several other phenotypes in SlIAA9 antisense lines of Micro-Tom (AS-IAA9) have been reported, e.g., hypersensitivity to auxin, enhanced hypocotyl/stem elongation, and reduced apical dominance were observed in AS-IAA9 plants (Wang et al, 2005); few studies have compared SlIAA9 knockout phenotypes in various tomato cultivars

Summary

Introduction

Tomato (Solanum lycopersicum) – a model horticultural crop – is one of the most important vegetable and fruit crops worldwide. In wild-type tomato plants, fruiting can be induced by artificial pollination and the application of exogenous auxin. Parthenocarpy, which allows fruit production without fertilization, is a hugely important agricultural trait and has been produced by traditional breeding in limited species and cultivars. The fruiting of tomato is controlled by auxin signaling factors, tomato Auxin Responsive Factor 8 (SlARF8), and the auxin responsive transcription repressor INDOLE-3-ACETIC ACID 9 (SlIAA9; Wang et al, 2005; Goetz et al, 2006). Loss-of-function mutants of SlIAA9 in tomato exhibit parthenocarpy – a desirable trait in tomato – where fruit set and growth are stimulated

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