Rice Non-Specific Phospholipase C6 Is Involved in Mesocotyl Elongation.

Mesocotyl elongation of rice is crucial for seedlings pushing out of deep soil. Underlying mechanisms on the phospholipid signaling in mesocotyl growth of rice are elusive. Here we report that the rice non-specific phospholipase C6 (OsNPC6) is involved in the mesocotyl elongation. Our results indicated that all five rice OsNPCs (OsNPC1, OsNPC2, OsNPC3, OsNPC4 and OsNPC6) hydrolyzed the substrate phosphatidylcholine (PC) to phosphocholine (PCho), and all of them showed plasma membrane localization. Overexpression (OE) of OsNPC6 produced plants with shorter mesocotyls, while comparing to those of Nipponbare (Nip) and npc6 mutants. Although the mesocotyl growth of npc6 mutants was not much affected without GA3, it was obviously elongated by the treatment of GA. Upon GA3 treatment, SLENDER RICE1 (SLR1), the DELLA protein of gibberellin (GA) signaling, was drastically increased in OE plants, in contrary, the level of SLR1 was found decreased in npc6 mutants. The GA-enhanced mesocotyl elongation and the GA-impaired SLR1 level in npc6 mutants were attenuated by the supplementation of PCho. Further analysis indicated that the GA-induced expression of phospho-base N-methyltransferase 1 (PMT1) in npc6 mutants was significantly weakened by the addition of PCho. In summary, our results suggest that OsNPC6 is involved in mesocotyl development via modulation of phosphocholine in rice.