Table 4.

Compilation of the function associated with type-A response regulators from different species

Species	Involved in /expression changed upon treatment with
Catharanthus roseus CrRR1, CrRR2, CrRR3	Upregulation by cytokinin, but not auxin, salt stress or ABA; induction was inhibited by blocking of the receptors (CrRR1)64; CrRR1 expression downregulated in CrHP1-antisense plants13; not transcript detected for CrRR2 but for CrRR313
Lotus japonicas LjRRa1, LjRRa2, LjRRa3, LjRRa4, LjRRa5, LjRRa6, LjRRa7	Upregulated by cytokinin20; (LjRRa5)63
Medicago trunculata MtRR3, MtRR4, MtRR5	Regulated by cytokinin11, upregulated by symbiosis (MtRR4)29; partially nod-factor-dependent (MtRR4 is dependent, MtRR5 not)11; upregulated in MtCRE1-RNAi-roots29
Oryza sativa OsRR1, OsRR2, OsRR3, OsRR4, OsRR5, OsRR6, OsRR7, OsRR8, OsRR9, OsRR10, OsRR11, OsRR12, OsRR13, OsRR14, OsRR15, OsRR41	Expression detected17,19,21,22,60; upregulated by cytokinin (OsRR1–11, 14)21,22,60; partially regulated by dehydration, salt stress and cold stress17, overexpressors of OsRR3 and OsRR5 with more lateral roots and longer roots on cytokinin, but more sensitive towards cytokinin in callus formation and chlorophyll content assay; several type-ARRs downregulated in overexpressors of OsRR3 and OsRR560; overexpressed GFP fusion with OsRR6 shows accumulation in cytosol; overexpressor of OsRR6 has a dwarfed, less branched phenotype, a less developed root system and is sterile59; Osrr9/Osrr10 knockout plants are dwarfed and sterile22
Phaseolus vulgaris PvRR1	Upregulation by cytokinin, and depletion of K, N and P; localized to the nucleus62
Pinus pinea PipiRR1	Upregulation by cytokinin61
Populus trichocarpa PtRR1, PtRR2, PtRR3, PtRR4, PtRR5, PtRR6, PtRR7, PtRR8, PtRR9, PtRR10, PtRR11	Expression detected23; PtRR7 strongly downregulated in pBpCRE1:AtCKX2 plants32
Zea maize ZmRR1/ZmCip1, ZmRR2, ZmRR3/ABPHYL1, ZmRR4, ZmRR5, ZmRR6, ZmRR7, ZmTcRR1, ZmTcRR2	Upregulated by cytokinin (ZmRR1, ZmRR2)9,56,57, (ZmRR1,4–7)41; upregulated by nitrate in resupplied leaves (ZmRR1)8,9,57, (ZmRR2)55,57 localized in the nucleus (ZmRR3–7) or in the cytosol (ZmRR1–3)41; interaction of ZmRR1 with ZmHP1, ZmHP2 and ZmHP341; in vitro phosphorylation of ZmRR4 by ZmHP1 and ZmHP241; knockout of ZmRR3 shows decussate leaf pattern and a bigger meristem51–53; ZmTcRR1 and ZmTcRR2 are unusual response regulators expressed in the transfer cell layer33,54
Vitis vinifera VvRRa1, VvRRa2, VvRRa3, VvRra4	Regulated by cytokinin (VvRRa3 up and VvRRa4 down in isolated cells)7