Genetic and signalling pathways of dry fruit size: targets for genome editing‐based crop improvement

Abstract

Summary Fruit is seed‐bearing structures specific to angiosperm that form from the gynoecium after flowering. Fruit size is an important fitness character for plant evolution and an agronomical trait for crop domestication/improvement. Despite the functional and economic importance of fruit size, the underlying genes and mechanisms are poorly understood, especially for dry fruit types. Improving our understanding of the genomic basis for fruit size opens the potential to apply gene‐editing technology such as CRISPR/Cas to modulate fruit size in a range of species. This review examines the genes involved in the regulation of fruit size and identifies their genetic/signalling pathways, including the phytohormones, transcription and elongation factors, ubiquitin‐proteasome and microRNA pathways, G‐protein and receptor kinases signalling, arabinogalactan and RNA‐binding proteins. Interestingly, different plant taxa have conserved functions for various fruit size regulators, suggesting that common genome edits across species may have similar outcomes. Many fruit size regulators identified to date are pleiotropic and affect other organs such as seeds, flowers and leaves, indicating a coordinated regulation. The relationships between fruit size and fruit number/seed number per fruit/seed size, as well as future research questions, are also discussed.

Phytohormones in fruit development and maturation

“…Increases in auxin similarly stimulate cell division in GA‐deficient tomato ( gib‐3 mutant lines) during early growth while applications of GA to auxin‐insensitive plants ( dgt mutant lines) have a minimal effect on cell division, which supports the notion that auxin is mainly necessary for the early cell proliferation phase (Liu et al ., 2016). With respect to GA, GA3ox is expressed during silique development in Arabidopsis in the replum, funiculus, and receptacle (Hussain et al ., 2020), and three distinct GA receptor genes ( CaGID1b . 1 , CaGID1b .…”

“…During fruit development, CKs bind to histidine kinases (HKs), which donate phosphate groups to downstream response elements via the action of AHPs. Consequently, a mutation reducing AHP activity results in CK insensitivity and smaller siliques, while attenuated CKX expression leads to increased CK and larger siliques (Hussain et al ., 2020). In Arabidopsis, as well as in strawberry, BRs function alongside other phytohormones in controlling fruit size.…”

“…In Arabidopsis, as well as in strawberry, BRs function alongside other phytohormones in controlling fruit size. Mutations in multiple enzymes within the BR biosynthetic pathway in Arabidopsis lead to shorter siliques (Hussain et al ., 2020) while downregulation of BR receptors in strawberries reduces cell division (Baghel et al ., 2019).…”

Genes, mechanisms and novel EST-SSR markers associated with metribuzin tolerance in wheat (Triticum aestivum L.): targets for improving photosynthetic capacity and yield

“…Glutathione metabolism removes free radicals and prevents oxidative damage to DNA, proteins and lipids. Ascorbic acid (antioxidant) functions as a cofactor for enzymes in photosynthesis, and the synthesis of plant hormones [19] and affects gene expression and transcription, cell division, and growth [20].…”

CRISPR-Cas9 Mediated Knockout of NtAn1 to Enhance the Lipid Accumulation in Tobacco Seed for Biodiesel Production

“…These genes include SP (SELF-PRUNING) [47], fw2.2 (FRUIT WEIGHT 2.2) [48], FASCIATED [49], and MULTIFLORA [50]. Previous studies had demonstrated that the genetic regulation networks of agronomic traits were conserved in different plant taxa, which suggested that editing the homolog genes across species may generate similar phenotypes [51]. We suggested that the domestication knowledge from model crops could be translated into tobacco for the generation of high seed yield and high lipid content varieties.…”