Regulating ABA level through GhABAH gene in transgenic cotton revealed their important roles in the growth and development of cotton plant and fiber cell

Functional Genomics

poster

Ye, Shue; Li, Fang; Wei, Ting; Zhai, Yunlan; Zeng, Zhifeng; Tang, Yingcai; Bai, Wenqin; Zhang, Mi; Pei, Yan; Luo, Ming

Ye, Shue

Luo, Ming

Abscisic acid (ABA) is one of the important classical phytohormones in plant kingdom. However, the role of ABA in the growth and development of cotton fiber is largely unknown to date though ABA was extracted firstly from cotton. To illuminate the role of ABA and related genes in cotton fibers, the ABA 8'-hydroxylase gene (GhABAH) was selected for creating transgenic cotton plants. GhABAH is a key enzyme involved in ABA catabolism. It expressed higher in root than in stem and leaf. At various developmental stages of fiber cell, there was a high expression level at the early stage of fiber elongation (6 DPA). With the increase of fiber elongation rate, the expression level was reduced gradually and reached the bottom at 12 DPA, which was a rapid elongation stage of fiber cell. Then with the decrease of fiber elongation rate, the expression level of GhABAH was increased and reached the top at 18 DPA in which the secondary cell wall started to deposit. These results revealed that the expression pattern of GhABAH is depended on the development of fiber cell. The content of ABA was detected and the phenotypic variation of transgenic cotton plants was characterized either in transgenic or wild type plants. Compared with wild type, the endogenous ABA content of transgenic cotton was reduced by 63.1%, and the transgenic plant were slender, branches were shorter, leaves and bolls were smaller, leaves were wilting, stomata can't close normally, blooming time was delayed, petals and sepals were smaller, pollen grain not spilled out, pollen sterility were reduced. Meanwhile, lateral root number was increased by 200% under the condition of 200 mM NaCl in seedling. On the contrary, suppressing GhABAH expression level led endogenous ABA level to increase by 54.4%, and increased ABA sensitivity in seedlings. These results indicated that modified the GhABAH expression level can affect plant endogenous ABA levels and the development of cotton plants. Over-expressing GhABAH inhibited fiber cell initiation and elongation in transgenic cotton. Mature fiber length of transgenic cotton was 2.64±0.03 cm. Compared with wild type, which fiber length was 2.97±0.02 cm, transgenic fiber was shortened by 11.1%, the secondary wall was thicker, the micronaire increased by 31%, the fiber strength reduced by 20%. At the same time, the transgenic cotton fibers were more resistant to ABA than that of wild type. However, suppressing GhABAH expression didn’t display obvious effect on the mature fiber length. Only the secondary wall was thicker significantly than wild type fibers. These results revealed that change of GhABAH expression level not only affected fiber differentiation, initiation and elongation, but also influenced the formation of the secondary wall, and proved that the gene play an important role in regulating the growth and development of cotton fiber.