抄録
Mesocotyl elongation in rice is essential for seedling emergence. Our previous screening identified two weedy rice accessions (Oryza sativa f. spontanea L.) (WR04-6 and WR04-43) were with unusually long mesocotyl. In this study, using rice cultivar (Nipponbare, Oryza sativa L., subspecies temperate japonica) as a control, we found that at the middle and end of mesocotyl elongation, the predominant cortical microtubules (CMTs) in weedy rice are transversely oriented that related to cell elongation, while, cultivated rice had oblique MT arrays. Interestingly, more extensive MT depolymerization was observed in the early stage of mesocotyl elongation in weedy rice accessions than that in cultivated rice. Moreover, MT-destabilizing agent oryzalin treatment (25 nM) led to an increase of rice mesocotyl length, which is correlated with mesocotyl cell elongation. On the contrary, MT-stabilizing agent taxol led to a full inhibition of weedy rice mesocotyl growth. Further, oryzalin treatments resulted in an endogenous gibberellin (GA) increase and the high expression of GA biosynthesis related gene-GA20ox2, GA3ox2, and GIBBERELLIN-INSENSITIVE DWARF1 (GID1), and taxol treatments had an opposite effect on the change of GA content and the GA biosynthesis gene expression. By contrast, the early CMT depolymerization in the weedy rice mesocotyl elongation was not affected by the change of GA content. Our findings suggested that an early depleted form of CMTs is a main reason of unusually long mesocotyls in weedy rice, and it plays an important role in rice mesocotyl growth, which has a close relationship with an increase of endogenous GAs.
