Nitrogen Deficiency Accelerates Rice Leaf Senescence Through ABA Signaling and Sugar Metabolic Shifts

Area of Science:

• Plant Physiology
• Molecular Biology
• Agricultural Science

Background:

• Nitrogen deficiency is a key driver of leaf senescence, impacting plant yield.
• The precise role of abscisic acid (ABA) signaling in regulating sugar metabolism and nitrogen allocation during senescence is not fully understood.

Purpose of the Study:

• To investigate how nitrogen (N) supply levels affect leaf carbon/nitrogen (C/N) allocation.
• To elucidate the relationship between ABA signaling, sugar metabolism, and N assimilation in rice under varying N conditions.

Main Methods:

• Utilized two rice genotypes under four distinct nitrogen treatments.
• Analyzed leaf C/N allocation, ABA signaling pathway components (PYL, ABA biosynthesis), sugar metabolism, N assimilation, and senescence-associated gene expression.

Main Results:

• N-deficiency significantly increased PYR1-like (PYL) expression and ABA biosynthesis, activating ABA signaling.
• Elevated ABA levels promoted sugar and N catabolism, reduced photosynthetic pigments, and intensified oxidative damage.
• ABA signaling upregulated senescence-associated genes (SAGs) and altered C/N allocation via transcription factors (NAC, bZIP, WRKY) and suppression of PP2Cs.

Conclusions:

• Nitrogen deficiency accelerates leaf senescence by impairing chlorophyll biosynthesis and promoting degradation through ABA signaling.
• This metabolic network highlights the interplay between sugar signaling, N assimilation, and N-use efficiency in regulating leaf senescence.