Differential expression of iron-sulfur cluster biosynthesis genes during peach fruit development and ripening, and their response to iron compound spraying

- Development of 'Xiahui8' peaches last for 130 days, followed by a rapid on-tree ripening within 7 days.
- Fe-S cluster biosynthesis gene expression was closely related to peach development, Fe nutriton and Fe metabolism.
- Fe fertilizer spraying mainly induced Fe-S cluster biosynthesis gene expression.
- Expression pattern of ISU1 and HSCA1 was distinct among different species.

Iron (Fe) is required for the iron-sulphur (Fe-S) cluster biosynthesis, which occurs in chloroplasts, mitochondria and cytosol that needs dozens of genes. However, molecular mechanisms of Fe metabolism in fruit trees are largely rare, especially towards fruit development and ripening. In this work, we characterized 'Xiahui8′ peach development, and analyzed expression profiles of 44 Fe-S cluster biosynthesis genes during different fruit development stages. The development of 'Xiahui8′ peaches last for an average period of 130 days, followed by a rapid on-tree ripening during 7 days. Notably, the Fe accumulation in peach flesh was negatively correlated to fruit weight and volume, but positively correlated to flesh firmness. Quantitative Real-Time PCR (qRT-PCR) analysis showed that Fe-S cluster biosynthesis genes were differentially expressed during distinct fruit development stages. A majority of plastid SUF and mitochondrial ISC machinery genes were gradually enhanced along with fruit growth, and began to decrease since commercial harvest phase. The highest expression level of all cytosolic CIA machinery genes were appeared in early fruitlet formation stage, and gradually reduced until fruit ripening. Moreover, foliar spraying of amino acid-Fe compound fertilizer significantly enhanced the total soluble solid (TSS) content in peaches, accompanied by strengthened flesh firmness, Fe concentration, and succinate dehydrogenase (SDH) and aconitase (ACO) activities. Thirteen Fe-S cluster biosynthesis genes were responsive to fertilizer treatment, whose expression level were significantly induced, with the exception of HSCA2 that was reduced. Our findings provided molecular basis for Fe metabolism in peach fruit development, and revealed potential genes for further functional verification.