Analysis about the role of ethylene in the low-pH-induced root hair formation in lettuce.

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High density of root hairs were induced on a lettuce root when a lettuce seedling was cultured at pH 4.Phytohormone ethylene mediated on this phenomenon. In this research, contribution of genes which encode ethylene synthesis enzyme and ethylene receptor was investigated. Two ACC synthase genes (named LsACSland LsACS2) and 4 ethylene receptor genes (named LsERSl, LsETRl, LsETR2 and LsETRS) were newly isolated from lettuce seedlings. Expression of ACSl increased about 2 times after 30 min to 2 hr after lowering of pH form 6 to 4.Expression of ACS2 increased about 3 times at 30 min after and reduced to the initial level within 1hr. Mediation of ethylene on the lowpEHnduced root hair formation was reconfirmed. on the point of ACC synthase gene expression.Irradiation of blue light for 3 to 6 hr was essential for the growth of root hairs. Expression of ACS1 was increased about 6 times by the 3hr blue light irradiation. Blue light had no effect on the expression ofACS2.Arrangement of cortical microtubules in a root epidermal cell was changed from perpendicular to random within 30 min after pH lowering. Application ofACC could induce the randomization of cortical microtubules.Considering the time course of genes expression and the effects of light on the genes expression, ACS2 mediated in the randomization of microtubules and initiation of root hair primordial and ACS1 mediated in the growth of root hairs.