RrTTG1 promotes fruit prickle development through an MBW complex in Rosa roxburghii

Abstract

Fruit prickles are widely distributed on the pericarp and exhibit polymorphic traits at different developmental stages. Although they are multicellular appendages that are well-known for helping plants defend against biotic and abiotic stresses, their origination and molecular mechanism are still less known. Here, we studied the origination and molecular mechanism of fruit prickles in Rosa roxburghii. Using morphological and histological observations, we found that the fruit prickle primordium of R. roxburghii originated from the ground meristem that underwent cell division to form flagelliform prickles, continued to enlarge, and finally lignified to form mature fruit prickles. We amplified a homolog of candidate gene TRANSPARENT TESTA GLABRA1 (TTG1) from R. roxburghii, named RrTTG1. RrTTG1 harbored four conserved WD-repeat domains and was exclusively nuclear-localized. Using qRT-PCR and in situ hybridization, we found that RrTTG1 was constitutively expressed and highly expressed during the initiation and cell expansion phases of fruit prickles. Ectopic expression analysis in Arabidopsis proved that RrTTG1 substantially enhanced the number of trichome and pigmentation production and inhibited root hair formation. Besides, RrTTG1 complemented the phenotypes of the ttg1 mutant in Arabidopsis, thus indicating that RrTTG1 played pleiotropic roles akin to AtTTG1. We demonstrated that the RrTTG1 only interacted with RrEGL3, a homolog of ENHANCER OF GLABRA3 (EGL3), via yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. Briefly, RrTTG1 might positively regulate the initiation of fruit prickle primordium and cell enlargement by forming the RrTTG1-RrEGL3-RrGL1 complex in R. roxburghii. Therefore, our results help characterize the RrTTG1 in R. roxburghii and also elucidate the establishment of the prickles regulatory system in the Rosaceae plants.

Genome-Wide Identification, Evolution, and Expression Analysis of the WD40 Subfamily in Oryza Genus

“…In addition to anthocyanin biosynthesis, studies have shown that TTG1 is also related to seed coat mucilage biosynthesis [33], root-hair pattern [34,35], flowering time regula-tion [36], fruit spine initiation [37,38]. Among other processes, TTG1 might also directly or indirectly regulate downstream target genes through interactions with other proteins [39].…”

Transcriptome Analysis Reveals Candidate Genes Involved in Gibberellin-Induced Fruit Development in Rosa roxburghii

“…Interestingly, The RNA-seq analyzed the transcripts of genes encoding R2R3 MYB and bHLH041 that were significantly up-regulated, showing that the conserved domains with RrGL1 and RrGL3/RrEGL3 might play similar effects on prickle development. However, RrTTG1 displayed no significant change in R. roxburghii, which explained why prickle only became longer but not numerous [17].…”

“…Regarding the glycolysis/gluconeogenesis pathway, the expression profiles of DEGs displayed two clusters. Among these, 32.69% of DEGs (17) were significantly enhanced in fruits after gibberellin application. For example, two unigene-encoded phosphoenolpyruvate carboxykinase were significantly raised.…”

“…Rosa roxburghii Tratt is also known as a chestnut rose belonging to the Rosaceae family. It is a deciduous, thick shrub that produces prickles on its stems and fruits [17]. Its fruits are widely consumed in China for their pleasant flavor and high nutrients.…”

The new directions in genetics, breeding and biotechnology of ornamental and berry crops in the N.I. Vavilov Institute of Plant Genetic Resources (VIR)

“…Роль гена TTG1 (Transparent Testa Glabra1), кодирующего транскрипционный фактор суперсемейства WD 40, в контроле развития трихом продемонстрирована для A. thaliana (Szymanski et al, 2000), Rosa roxburghii Tratt. (Huang et al, 2022), R. rugosa Thunb. (Wang et al, 2019), Cucumis sativus L. и других двудольных растений (Shvachko et al, 2020).…”