Involved in autophagy in a nutritional condition dependent manner. The ATG1-ATG13 protein kinase complex regulates downstream events required for autophagosome enclosure and/or vacuolar delivery. Becomes a target of autophagy under nutrient starvation. Connects autophagy to plant nutritional status. Interacts with ATG1A (PubMed:21984698). Interacts with ATG11 and ATG101 (PubMed:24563201). A number of isoforms are produced. According to EST sequences. Phosphorylated during nutrient starvation. Dephosphorylated in nutrient-rich conditions. No visible phenotype under normal growth conditions. The double mutant plants atg13a-1 and atg13b-2, or atg13a-2 and atg13b-2 are hypersensitive to nitrogen or carbon starvation and show early senescence. Belongs to the ATG13 family. Plant subfamily.