Lily Cdc42/Rac-interactive binding motif-containing protein, a Rop target, involves calcium influx and phosphoproteins during pollen germination and tube growth.
We report unique desiccation-associated ABA signaling transduction through which the Rop (Rho GTPase of plants) and its target LLP12-2 are regulated during the stage of pollen maturation and tube growth. Overexpression of LLP12-2 drastically inhibited pollen germination and tube growth. Studies on the germination inhibitors, Ca (2+) influx blocking agents LaCl 3 and EGTA and an actin-depolymerizing drug, latrunculin B (LatB), revealed that the LLP12-2-induced inhibition of germination and tube growth is significantly suppressed by LaCl 3 and EGTA in the LLP12-2-overexpressing pollen but not by LatB. These results suggested that LLP12-2 is associated with Ca (2+) influx in the cytoplasm and may be not with actin assembly. With the addition of LaCl 3 and EGTA, LLP12-2-overexpressing pollen increased germination and tube growth compared with the one without addition, whereas pollen expressing GFP decreased germination and tube growth. Thus, an optimum level of [Ca (2+) ]cyt influx is crucial for normal germination and tube growth. Studies on the inhibitors, staurosporine and okadaic acid in the LLP12-2-overexpressing pollen, showed no appreciable increase in germination when compared with the one without addition, suggesting that staurosporine-sensitive protein kinases and dephosphorylation of phosphoproteins may be not involved in the LLP12-2 mediated germination. However, the LLP12-2-induced inhibition of tube length was slightly but significantly suppressed by staurosporine, suggesting that staurosporine-sensitive protein kinases involve in the LLP12-2-induced inhibition of tube growth.
Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan.
Ssu-Wei
SW
Hsu
Co-Shine
CS
Wang
D000040:Abscisic Acid / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000502:physiology; D007811:Lanthanum / Q000494:pharmacology; D019319:Okadaic Acid / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D011058:Pollen / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014867:Water / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D010750:Phosphoproteins; C028521:lanthanum chloride; D014867:Water; D019319:Okadaic Acid; D004533:Egtazic Acid; D007811:Lanthanum; D000040:Abscisic Acid; D020764:cdc42 GTP-Binding Protein; D002118:Calcium