Abstract: Plants employ sophisticated mechanisms to recycle intracellular constituents needed for growth , development , and survival under nutrient-limiting conditions .
Autophagy is one important route in which cytoplasm and organelles are sequestered in bulk into vesicles and subsequently delivered to the vacuole for breakdown by resident hydrolases .
The formation and trafficking of autophagic vesicles are directed in part by associated conjugation cascades that couple the AUTOPHAGY-RELATED8 ( ATG8 ) and ATG12 proteins to their respective targets , phosphatidylethanolamine and the ATG5 protein .
To help understand the importance of autophagy to nutrient remobilization in cereals , we describe here the ATG8/12 conjugation cascades in maize ( Zea mays ) and examine their dynamics during development , leaf senescence , and nitrogen and fixed-carbon starvation .
From searches of the maize genomic sequence using Arabidopsis ( Arabidopsis thaliana ) and rice ( Oryza sativa ) counterparts as queries , we identified orthologous loci encoding all components necessary for ATG8/12 conjugation , including a five-member gene family expressing ATG8 .
Alternative splicing was evident for almost all Atg transcripts , which could have important regulatory consequences .
In addition to free ATG8 , its membrane-associated , lipidated form was detected in many maize it issues , suggesting that its conjugation cascade is active throughout the plant at most , if not all , developmental stages .
Levels of Atg transcripts and/or the ATG8-phosphatidylethanolamine adduct increase during leaf senescence and nitrogen and fixed-carbon limitations , indicating that autophagy plays a key role in nutrient remobilization .
The description of the maize ATG system now provides a battery of molecular and biochemical tools to study autophagy in this crop under field conditions .
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