Morphological and anatomical characteristics of exserted stigma sterility and the location and function of SlLst (Solanum lycopersicum Long styles) gene in tomato.

KEY MESSAGE: Anatomical changes in and hormone roles of the exserted stigma were investigated, and localization and functional analysis of SlLst for the exserted stigma were performed using SLAF-BSA-seq, parental resequencing and overexpression of SlLst in tomato. Tomato accession T431 produces stigmas under relatively high temperatures (> 27 °C, the average temperature in Harbin, China, in June-August), so pollen can rarely reach the stigma properly. This allows the percentage of male sterility exceed 95%, making the use of this accession practical for hybrid seed production. To investigate the mechanism underlying the exserted stigma male sterility, the morphological changes of, anatomical changes of, and comparative endogenous hormone (IAA, ABA, GA3, ZT, SA) changes in flowers during flower development of tomato accessions DL5 and T431 were measured. The location and function of genes controlling exserted stigma sterility were analyzed using super SLAF-BSA-seq, parental resequencing, comparative genomics and the overexpression of SlLst in tomato. The results showed that an increase in cell number mainly caused stigma exsertion. IAA played a major role, while ABA had an opposite effect on stigma exertion. Moreover, 26 candidate genes related to the exserted stigma were found, located on chromosome 12. The Solyc12g027610.1 (SlLst) gene was identified as the key candidate gene by functional analysis. A subcellular localization assay revealed that SlLst is targeted to the nucleus and cell membrane. Phenotypic analysis of SlLst-overexpressing tomato showed that SlLst plays a crucial role during stigma exsertion.

The α-Subunit of the Chloroplast ATP Synthase of Tomato Reinforces Resistance to Gray Mold and Broad-Spectrum Resistance in Transgenic Tobacco.

Chloroplast ATP synthase (cpATPase) is responsible for ATP production during photosynthesis. Our previous studies showed that the cpATPase CF1 α subunit (AtpA) is a key protein involved in Clonostachys rosea-induced resistance to the fungus Botrytis cinerea in tomato. Here, we show that expression of the tomato atpA gene was upregulated by B. cinerea and Clonostachys rosea. The tomato atpA gene was then isolated, and transgenic tobacco lines were obtained. Compared with untransformed plants, atpA-overexpressing tobacco showed increased resistance to B. cinerea, characterized by reduced disease incidence, defense-associated hypersensitive response-like reactions, balanced reactive oxygen species, alleviated damage to the chloroplast ultrastructure of leaf cells, elevated levels of ATP content and cpATPase activity, and enhanced expression of genes related to carbon metabolism, photosynthesis, and defense. Incremental Ca2+ efflux and steady H+ efflux were observed in transgenic tobacco after inoculation with B. cinerea. In addition, overexpression of atpA conferred enhanced tolerance to salinity and resistance to the fungus Cladosporium fulvum. Thus, AtpA is a key regulator that links signaling to cellular redox homeostasis, ATP biosynthesis, and gene expression of resistance traits to modulate immunity to pathogen infection and provides broad-spectrum resistance in plants in the process.