Abstract: 【Objective】 The objective of this study is to analyze the transcriptional expression of KT/HAK/KUP family genes and response characteristics to potassium fertilizer application during different flowering stages, and key K⁺ transporter genes and its function. A close relationship between K⁺ nutritional status and flower development was discussed, thus providing a theoretical basis for K fertilization in orchards and genetic improvement and breeding of efficient horticulture crops.【Method】The K fertilizer treatment experiment was conducted via applying 834 g KCl (K₂O content 60%) to each ‘Xiahui6’ peach tree at flower bud expanding stage. The effect of K fertilizer application on flower development, K⁺ nutritional status and blooming date of peach trees was analyzed. The K⁺ concentration of peach flowers at different developmental stages was determined by using ICP-AES apparatus with HNO₃-HClO₄ digestion method. Quantitative real-time PCR was used to analyze the expression profiles of KT/HAK/KUP family genes during the whole flowering process, and the key K⁺ transporter genes were identified. The response of KT/HAK/KUP family genes to K fertilizer application at different developmental stages was also revealed. Functions of the key genes were validated by using heterologous complementation of bacterial function lossing mutant. Coding sequence of KUP11 was cloned into pPAB404 vector to obtain the recombinant expression vector pPAB404-KUP11. Sequencing verified recombinant vector was then transformed into functional mutant E. coli strain TK2420. Whether the recombinant vector pPAB404-KUP11 can restore the ability of TK2420 mutant strain to uptake external K⁺, supplied with either KCl or K₂SO₄, was determined.【Result】Application of K fertilizer treatment favorably induced ‘Xiahui6’ flowers to bloom 2-day earlier, and specifically contributed to flower development at full bloom stage, with an increase of 21.5% in fresh weight. The highest K⁺ accumulation occurred at full-bloom stage, which was followed by begin bloom, bud period and petal fall stages. Potasium application significantly enhanced the K⁺ nutritional status, with an increase of 24.3%, 27.4%, 29.1% and 26.3% of K⁺ concentration, respectively, during four flowering stages. Genes of KUP1-13 were differentially expressed during the four stages, and the highest expression level appeared especially in full-bloom stage. The KT/HAK/KUP family genes were differentially regulated by K, i.e., KUP1 and KUP5 were most sensitive to Kapplication, whose expression was consistently induced from bud swell stage to full-bloom stage. KUP11 was the most expressed gene throughout the whole flowering process, which was highly up-regulated at bud swell stage but greatly reduced at petal fall stage by K treatment. The recombinant expression vector pPAB404-KUP11 can restore the K⁺ uptake capacity in TK2420 bacterial mutant, and can utilize either external KCl or K₂SO₄, indicating that the expression level of KUP11 was positively correlated with the K⁺ uptake of bacterial cells.【Conclusion】Application of K fertilizer favorably promotes peach flower development, improves the K⁺ nutritional status, makes peach flower early to open, and differentially regulated KT/HAK/KUP family genes at different flowering stages. KUP11 transporter possesses the capacity to uptake external K⁺, which may play an important role in peach flowering.

Key words: peach, flowering, potassium, KT/HAK/KUP gene family, potassium homeostasis, peach, flowering, potassium, KT/HAK/KUP gene family, potassium homeostasis