Necessary for chloroplast and nuclear photorelocation movements via the regulation of chloroplast-actin (cp-actin) filaments in mesophyll cells, and together with PMIR1, in pavement cells (PubMed:26324877). Required component for both the low- and high-light-dependent chloroplast movement responses via an abscisic acid (ABA) pathway (PubMed:16113226, PubMed:25154696). Involved in the ABA response pathway during seed germination. Modulates ABA accumulation during periods of water deficit at the seedling stage (PubMed:25154696). Expressed in leaves, stems, cauline leaves, and flowers but not in roots (PubMed:16113226). Present in leaves in both mesophyll and pavement cells (PubMed:26324877). Repressed by osmotic stress (300 mM mannitol). Severely attenuated chloroplast movements under low- and high-light fluence, leading to evenly distributed chloroplasts in leaf mesophyll in pmi1-1 (PubMed:16113226, PubMed:25154696). Severe defects in both chloroplast and nuclear photorelocation movements resulting from the impaired regulation of chloroplast-actin filaments in pmi1-5 (PubMed:26324877). Reduced response to water-deficit and abscisic acid (ABA) treatments. The mutants pmi1-3 and pmi1-4 are hypersensitive to ABA during seed germination, but not pmi1-1, which is hyposensitive. Chloroplasts of pmi1-3 have altered chloroplast movements in low light (PubMed:25154696). Truncated N-terminus.