Bulk RNA-sequencing of hypocotyl explant-derived calli of Arabidopsis WT and rap2.12-2
Plants are aerobic organisms that rely on molecular oxygen for respiratory energy production. Hypoxic conditions, with oxygen levels ranging between 1% and 5%, usually limit aerobic respiration and affect plant growth and development. Here, we demonstrate that hypoxic microenvironment induced by active cell proliferation during the two-step plant regeneration process intrinsically represses the regeneration competence of callus in Arabidopsis thaliana. Hypoxia-repressed plant regeneration was mediated by the RELATED TO APETALA 2.12 (RAP2.12) protein, a member of the Ethylene Response Factor VII (ERF-VII) family. The hypoxia-activated RAP2.12 protein promoted salicylic acid (SA) biosynthesis and defense responses, inhibiting pluripotency acquisition and de novo shoot regeneration in calli. RAP2.12 could bind directly to the SALICYLIC ACID INDUCTION DEFICIENT 2 (SID2) gene promoter and activate SA biosynthesis, repressing plant regeneration via a PLETHORA (PLT)-dependent pathway. The rap2.12 mutant calli exhibited enhanced shoot regeneration, which was impaired by SA treatment. Taken together, our findings demonstrate that cell proliferation-dependent hypoxic microenvironment reduces cellular pluripotency and plant regeneration through the RAP2.12–SID2 module. Overall design: Hypocotyls of 1-week-old Col-0 (WT) and rap2.12-2 Arabidopsis thaliana seedlings were excised and incubated on callus-inducing medium (CIM). Calli were collected 7 days after incubation on CIM. Three biological replicates for each sample were generated.