Mitogen-activated protein kinases associated sites of tobacco REPRESSION
OF SHOOT GROWTH regulates its localization in plant cells
Abstract
RSG was involved in plant gibberellin feedback regulation by inducing
the expression of key genes. The tobacco calcium-dependent protein
kinase, CDPK1 was reported to interact with RSG and manipulate its
intracellular localization by phosphorylating Ser-114 of RSG. Here, we
identified tobacco mitogen-activated protein kinase 3 (NtMPK3) as an RSG
interacted protein kinase. Mutation of predicted MAPK-associated
phosphorylation site of RSG (Thr-30, Ser-74 and Thr-135) significantly
altered the intracellular localization of NtMPK3-RSG interaction
complex. Nuclear transport of RSG and its amino acids mutants (T30A and
S74A) were observed after treated with plant defense elicitor peptide
flg22 in 5 min, while the two mutated RSG swiftly relocalized in tobacco
cytoplasm in 30 min. Moreover, triple points mutation of RSG
(T30A/S74A/T135A) mimics constant unphosphorylated status, and
predominantly localized in tobacco cytoplasm. RSG (T30A/S74A/T135A)
showed no relocalization effect under the treatments of either flg22, B.
cereus AR156 or GA3, and was impaired in its role as TFs. Our results
suggest that MAPK associated phosphorylation sites of RSG regulate its
localization in tobacco and constant unphosphorylation of RSG in Thr-30,
Ser-74 and Thr-135 keeps RSG predominantly localized in cytoplasm.