Tissue- and environmental response-specific expression of 10 PP2C transcripts in Mesembryanthemum crystallinum

Abstract

Ten transcripts (Mpc1-10) homologous to protein phosphatases of the 2C family have been isolated from the halophyte Mesembryanthemum crystallinum (common ice plant). Transcripts range in size from 1.6 to 2.6 kb, and encode proteins whose catalytic domains are between 24% and 62% identical to that of the Arabidopsis PP2C, ABI1. Transcript expression is tissue speci®c. Two isoforms are present only in roots (Mpc1 and Mpc5), three in young leaves (Mpc6, 8 and 9), two in old leaves (Mpc6 and Mpc8), and two in post-¯ow-ering leaves (Mpc8 and Mpc9). Mpc2 is strongly expressed in roots and also in seeds, meristematic tissues and mature¯owers. Mpc3 is speci®c for leaf meristems, and Mpc4 is found in root and leaf meristems. Mpc7 is restricted to meristematic tissues. Mpc10 is only present in mature¯owers. Mpc2 (in roots and leaves), Mpc5 (in roots) and Mpc8 (weakly in leaves) are induced by salinity stress and drought conditions with dierent kinetics in dierent tissues, but other Mpcs are downregulated by stress. Cold stress (4°C) leads to a decline in Mpc5 and Mpc6, but low temperature provoked a longterm (days) increase in Mpc2 levels in leaves and a transient increase (less than 24 h) in roots. Four fulllength transcripts have been obtained. In each case, after over-expression in E. coli, the isolated proteins exhibited (Mg 2+ -dependent, okadeic acid-insensitive) protein phosphatase activity, although activity against 32 P-phosphocasein varied among dierent PP2Cs. Determination of tissue developmental and stress response speci®city of PP2C will facilitate functional studies of signal-transducing enzymes in this halophytic organism.

The dsRNA-binding protein DRB4 interacts with the Dicer-like protein DCL4 in vivo and functions in the trans-acting siRNA pathway

“…Membranes were washed three times in 2 · SSC with 0.5% SDS at 38°C for 1 h (DNA probe) or at 55°C for 1 h (LNA probe), and then analyzed by the BAS 1500 imaging analyzer (Fuji Film). Total RNAs were isolated from about 0.1-0.5 g of Arabidopsis leaves or floral inflorescences by the aurintricarboxylic acid (ATA) method (Nagy et al 1988), and then Northern blot hybridization for mRNAs was performed as described previously (Miyazaki et al 1999). …”

Characterization of a Novel Plant PP2C-like Protein Ser/Thr Phosphatase as a Calmodulin-binding Protein

“…In plants, it has been demonstrated that plant PP2Cs play a role as negative regulators of drought, salinity, and cold-stress signaling (27,35,(43)(44)(45). Despite accumulating evidence indicating that PP2C-related phosphatases are pivotal regulators in signaling cascades, little is known about the regulation of enzymatic activity.…”

Molecular cloning and characterization of a rice PP2C,OsPP2C4

“…Moreover, kinase associated protein phosphatase (KAPP) is known to be an important element in flower meristem development (Stone et al, 1994;Williams et al, 1997;Stone et al, 1998) and an alfalfa PP2C, MP2C, has been found to act as a negative regulator of a stress activated MAPK (Meskiene et al, 1998). In addition, ten PP2C transcripts, Mpcl-MpclO, of ice plant showed tissue-and environmental response-specific expression patterns (Miyazaki et al, 1999). Besides these, it was reported *Corresponding author; fax +82-54-279-2199 e-mail genean@postech.ac.kr that Ptc2p/Ptc3p of budding yeast dephosphorylated the major cyclin dependent kinase, Cdc28p, and Ptc4 of fission yeast was involved in the regulation of vacuole fusion (Cheng et al, 1999;Gaits and Russel, 1999).…”