Functional Genomics
A cotton annexin protein AnxGb6 regulates fiber elongation under calcium signal stimulus
KAIJING ZUO, Yuqun HUANG
Annexins are assumed to be involved in regulating cotton fiber elongation, but direct evidence remain to be presented. Here we cloned six Annexin genes (AnxGb) abundantly expressed in fiber from sea-island cotton (G. barbadense). qRT-PCR results indicate that all six G. barbadense annexin genes are expressed in elongating cotton fibers, while only the expression of AnxGb6 was cotton fiber-specific. Yeast two hybridization and BiFC analysis revealed that AnxGb6 homodimer interacts with a cotton fiber specific actin GbAct1. Ectopic-expressed AnxGb6 in Arabidopsis enhanced its root elongation without increasing the root cell number. Ectopic AnxGb6 expression resulted in more F-actin accumulation in the basal part of the root cell elongation zone. Analysis of AnxGb6 expression in three cotton genotypes with different fiber length confirmed that AnxGb6 expression is correlated to cotton fiber length, especially fiber elongation rate. Our results demonstrate that AnxGb6 is important for fiber elongation by potentially providing a domain for F-actin organization.