Seedless citrus breeding requires male sterility. Citrus hybrid breeding is inefficient due to its lengthy juvenile phase and nucellar polyembryony. For more than 30 years, the citrus research group at Huazhong Agricultural University’s National Key Laboratory for Germplasm Innovation and Utilization of Horticultural Crops has worked on cell engineering and genetic improvement. The examination bunch has effectively recovered seedless citrus hybrids, including G1+HBP and G1+STY, through physical cell combination. The method shortens the breeding cycle by at least 20 years by transferring mitochondrion from Satsuma mandarin (G1), a cytoplasmic male sterile (CMS) cultivar, to seedy pummelos (HBP, STY).
Cybrid citrus’ mitochondrial genome (G1 + HBP) comes from the CMS callus parent “Guoqing No. The nuclear and chloroplast genomes of G1 + HBP come from the fertile mesophyll parent Hirado Buntan pummelo (HBP), whereas those of 1” Satsuma mandarin (G1) are from HBP. The tree of G1+HBP looks like HBP, as well as organic product appearance and flavor, while G1+HBP showed common male sterility, including declined petals and stamens and cut-short dust, which brought about seedless organic product.
The communication of mitochondrion from CMS parent G1 and core from HBP could contribute to male sterility in G1+HBP. The male sterility-up-and-comer qualities of the cybrid were distinguished utilizing similar examination of omics and the mitochondrial genome, while the connection example of mitochondrion and atomic in this cybrid is as yet unclear.
“Spatiotemporal profiles of gene activity in stamen delineate nucleo-cytoplasmic interaction in a male-sterile somatic cybrid citrus” is the title of the article that was published in Horticulture Research.
Using laser microdissection, the morphology of stamen organs and cell types at five crucial stages was observed and confirmed in this study. RNA-Seq was used to profile the genes’ expression in citrus stamens over time and space.
In G1+HBP stamen primordia, meiocytes, and microspores, differentially expressed genes (DEGs) related to stamen development were discovered. ABCE model qualities were efficiently examined, and B-class quality CgAP3.2, a recently distinguished AP3 homologous in citrus, was chosen as the up-and-comer quality engaged with stamen improvement, as per quality articulation and a protein connection measure.
The brokenness of mitochondria in G1+HBP was explained, and nucleo-cytoplasmic associations were proposed in light of the GO improvement examination of DEGs, estimation of chemicals, and essential digestion content of the bloom bud. The metabolism of auxin (IAA) and jasmonic acid (JA) was disrupted in G1+HBP stamen primordia. What’s more, the articulation example of DEGs connected with the JA digestion pathway, photosynthesis, and Krebs cycle (TCA) was steady.
Possible model of core mitochondrial connection connected with cytoplasmic male sterility in citrus hybrid. Credit: Horticulture Research
The abnormal photosynthesis in chloroplasts caused by the exogenous mitochondrion may disrupt IAA metabolism directly and affect JA metabolism indirectly, both of which alter the expression of genes related to stamen primordia development. Breath and mitochondrial-related cell parts were disturbed in meiocytes of G1+HBP, and mitochondrial nucleobase digestion was upset in microspores of G1+HBP, which together showed that the brokenness of mitochondria could influence meiosis and microspore improvement and bring about dust fetus removal.
Citrus cytoplasmic male sterility is supported by this study’s hypothesis of a possible nucleo-cytoplasmic interaction network in the stamen.
More information: Nan Jiang et al, Spatiotemporal profiles of gene activity in stamen delineate nucleo-cytoplasmic interaction in a male sterile somatic cybrid citrus, Horticulture Research (2023). DOI: 10.1093/hr/uhad105
