Guard cell‐specific inhibition of Arabidopsis MPK3 expression causes abnormal stomatal responses to abscisic acid and hydrogen peroxide

Abstract

Summary• MAP kinases have been linked to guard cell signalling. Arabidopsis thaliana MAP Kinase 3 (MPK3) is known to be activated by abscisic acid (ABA) and hydrogen peroxide (H 2 O 2 ), which also control stomatal movements.• We therefore studied the possible role of MPK3 in guard cell signalling through guard cell-specific antisense inhibition of MPK3 expression.• Such transgenic plants contained reduced levels of MPK3 mRNA in the guard cells and displayed partial insensitivity to ABA in inhibition of stomatal opening, but responded normally to this hormone in stomatal closure. However, ABA-induced stomatal closure was reduced compared with controls when cytoplasmic alkalinization was prevented with sodium butyrate. MPK3 antisense plants were less sensitive to exogenous H 2 O 2 , both in inhibition of stomatal opening and in promotion of stomatal closure, thus MPK3 is required for the signalling of this compound. ABAinduced H 2 O 2 synthesis was normal in these plants, indicating that MPK3 probably acts in signalling downstream of H 2 O 2 .• These results provide clear evidence for the important role of MPK3 in the perception of ABA and H 2 O 2 in guard cells.

Plant Aquaporin AtPIP1;4 Links Apoplastic H2O2 Induction to Disease Immunity Pathways

“…Despite different biochemical natures, both PAMPs commonly require AtPIP1;4 to induce PTI responses, except for the absence of induced MPK6 expression. This result is in line with previous findings that the MAPK cascade diverges at MPK3 and MPK6 (Asai et al, 2002;Bigeard et al, 2015) to regulate distinct substrates in response to different PAMPs (Galletti et al, 2011;Pitzschke, 2015) and that induced expression of MPK3 represents a circuit of the MAPK cascade in response to H 2 O 2 (Gudesblat et al, 2007).…”

MAP kinases MPK9 and MPK12 are preferentially expressed in guard cells and positively regulate ROS-mediated ABA signaling

“…Transgenic Arabidopsis plants in which MPK3 expression is reduced by 25% showed impaired ABA inhibition of stomatal opening and H 2 O 2 induced stomatal closure, whereas ABA promotion of stomatal closure and ABA-induced H 2 O 2 production were not affected. This finding suggests that MPK3 may function downstream of ROS in ABA inhibition of stomatal opening but not in ABA-induced stomatal closure (40). In contrast, our data indicate that MPK9 and MPK12 act downstream of ROS in both ABA inhibition of stomatal opening and ABA promotion of stomatal closure (Fig.…”

Disentangling the Complexity of Mitogen-Activated Protein Kinases and Reactive Oxygen Species Signaling

“…MPK3, MPK4, and MPK6 are activated by ABA and H 2 O 2 (for review, see Nakagami et al, 2005;Pitzschke and Hirt, 2006). In an elegant approach, the role of MPK3 in stomatal regulation has been investigated through guard cell-specific antisense inhibition of MPK3 expression (Gudesblat et al, 2007 (Gudesblat et al, 2007). However, provided that exogenously applied H 2 O 2 is qualitatively comparable to H 2 O 2 accumulating in response to ABA, MPK3 deficiency would be expected to also affect ABA-induced stomatal closure.…”