Overexpression of an ethylene-forming ACC oxidase (ACO) gene precedes the Minute Hilum seed coat phenotype in Glycine max

Abstract

Background To elucidate features of seed development, we investigated the transcriptome of a soybean isoline from the germplasm collection that contained an introgressed allele known as minute hilum (mi) which confers a smaller hilum region where the seed attaches to the pod and also results in seed coat cracking surrounding the hilum region. Results RNAs were extracted from immature seed from an extended hilum region (i.e., the hilum and a small ring of tissue surrounding the hilum in which the cracks form) at three different developmental stages:10–25, 25–50 and 50–100 mg seed fresh weight in two independent replicates for each stage. The transcriptomes of these samples from both the Clark isoline containing the mi allele (PI 547628, UC413, iiR t mi G), and its recurrent Clark 63 parent isoline (PI 548532, UC7, iiR T Mi g), which was used for six generations of backcrossing, were compared for differential expression of 88,648 Glyma models of the soybean genome Wm82.a2. The RNA sequence data obtained from the 12 cDNA libraries were subjected to padj value < 0.05 and at least two-fold expression differences to select with confidence genes differentially expressed in the hilum-containing tissue of the seed coat between the two lines. Glyma.09G008400 annotated as encoding an ethylene forming enzyme, ACC oxidase (ACO), was found to be highly overexpressed in the mi hilum region at 165 RPKMs (reads per kilobase per million mapped reads) compared to the standard line at just 0.03 RPKMs. Evidence of changes in expression of genes downstream of the ethylene pathway included those involved in auxin and gibberellin hormone action and extensive differences in expression of cell wall protein genes. These changes are postulated to determine the restricted hilum size and cracking phenotypes. Conclusions We present transcriptome and phenotypic evidence that substantially higher expression of an ethylene-forming ACO gene likely shifts hormone balance and sets in motion downstream changes resulting in a smaller hilum phenotype and the cracks observed in the minute hilum (mi) isoline as compared to its recurrent parent.

Characterization of the Common Genetic Basis Underlying Seed Hilum Size, Yield, and Quality Traits in Soybean

“…Interestingly, based on the physical positions of flanking markers, qSH6.2 mapped closely with the T locus (Hilum color 2-g1) and qSH10 mapped closely with E2. Meanwhile, a recent report revealed that two Clark isolines with contrasted genotype at T locus displayed significant different in phenotype of hilum size ( Zabala et al, 2020 ). Therefore, we hypothesize that qSH6.2 and qSH10 might be regulated by T and E2 , respectively.…”

Ethylene signaling plays an important role in UV-B-induced ascorbic acid accumulation in Cucumis Sativus leaves

“…Recent studies have shown that UV-B could promote the expression of ethylene synthesis genes and ethylene accumulation in plants (Naraet al, 2002;Pan et al, 2014;Mannucci et al, 2020). In particular, 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and the catalysis of ACC oxidase (ACO) are important rate-limiting enzymes for ethylene biosynthesis (Chae et al, 2005;Zabala et al, 2020). The ethylene receptor (ETR) senses ethylene, and, through a series of signal transduction steps, the downstream gene expression is finally regulated by the ethylene response factor (ERF) and combined with the GCCbox, DRE, CE1 and as-1 cis-elements of the promoter region of downstream genes (Wu et al, 2008;Lee et al, 2015).…”

Genome-Wide Identification and Functional Investigation of 1-Aminocyclopropane-1-carboxylic Acid Oxidase (ACO) Genes in Cotton

“…In carnation, ACO gene expression can be induced during flowering, pollination, and petal senescence [ 17 , 18 ]. In soybean, Zabala et al hypothesized that the overexpression of an ACO gene precedes the development of minute hilum seed coat phenotype [ 19 ].…”