AUTHOR=Wen Binbin , Gong Xingyao , Tan Qiuping , Zhao Wenzhe , Chen Xiude , Li Dongmei , Li Ling , Xiao Wei 

TITLE=MdNAC4 Interacts With MdAPRR2 to Regulate Nitrogen Deficiency-Induced Leaf Senescence in Apple (Malus domestica)

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.925035

DOI=10.3389/fpls.2022.925035

ISSN=1664-462X

ABSTRACT=<p>Nitrogen (N) is one of the important macronutrients in plants, and N deficiency induces leaf senescence. However, the molecular mechanism underlying how N deficiency affects leaf senescence is unclear. Here, we report an apple NAC TF, MdNAC4, that participates in N deficiency-induced leaf senescence. The senescence phenotype of apple leaves overexpressing <italic>MdNAC4</italic> was enhanced after N deficiency. Consistently, the chlorophyll content of transgenic leaves was significantly lower than that in the WT control leaves, the expression of chlorophyll catabolism-related genes (<italic>MdNYC1</italic>, <italic>MdPAO</italic>, and <italic>MdSGR1</italic>) was significantly higher than that in the WT controls, and the expression of chlorophyll synthesis-related genes (<italic>MdHEMA</italic>, <italic>MdCHLI</italic>, and <italic>MdCHLM</italic>) was significantly lower than that in the WT control leaves. Furthermore, MdNAC4 was found to directly activate the transcription of the chlorophyll catabolism-related genes <italic>MdNYC1</italic> and <italic>MdPAO</italic>. Additionally, MdNAC4 was proven to interact with MdAPRR2 proteins both <italic>in vitro</italic> and <italic>in vivo</italic>, and overexpression of <italic>MdAPRR2</italic> seemed to delay N deficiency-induced leaf senescence. Correspondingly, the chlorophyll loss of MdAPRR2-overexpressing (MdAPRR2-OE) lines was significantly lower than in WT control plants. Although downregulated, the expression of the chlorophyll synthesis-related genes <italic>MdHEMA</italic>, <italic>MdCHLI</italic>, and <italic>MdCHLM</italic> in the transgenic plants was more than twice that in the WT control plants. Taken together, our results enrich the regulatory network of leaf senescence induced by N deficiency through the interaction between MdNAC4 and MdAPRR2.</p>