Genome-wide Study Of ALMT Gene Family In Dendrobium Catenatum And Analysis Of Expression Profiles During Day And Night

Aluminum-activated malate transporters（ALMT）gene family play a vital role in stomatal movement.The ALMT gene family had been researched in many C3 and C4 plant,but little information was available about the ALMT gene family in CAM plant.Dendrobium catenatum was a typical facultative CAM plant.The important feature of CAM plant was that the stomata were closed during the day and opened at night.However,the role of ALMT gene family in the stomata behavior of the CAM was still unclear.In this study,we identified ALMT family members and analyzed sequence characteristics,gene structure,phylogenetic evolution,and circadian expression patterns of ALMT genes.The main results are as follows:（1）We identified 12 DcaALMT family members in D.catenatum based on the Arabidopsis thaliana ALMT protein sequence.The results showed that most of the DcaALMT genes consisted of 6 exons however Dca006649 contained only 4 exons.It presumed that DcaALMT gene family may take the way of losing exons to participate in the stomatal behavior of the CAM.（2）14 and 12 members of the ALMT gene family were identified in A.thaliana and D.catenatum.The number of DcaALMT genes related to stomatal movement decreased,which may be caused by the stomatal behavior of D.catenatum in the facultative CA M.There were fewer ALMT genes in Phalaenopsis equestris and Ananas comosus than in D.catenatum.From the perspective of photosynthetic efficiency and dry matter accumulation,the CAM,as a photosynthetic metabolic pathway evolved under the stress of plants,was not a high-yield choice for plants,so a shrinkage of gene families related t o photosynthesis had occurred.（3）Phylogenetic relationship analysis of ALMT genes from C3 and CAM plants showed that the gene families can be divided into five clades.Most of the ALMT genes from CAM plants are located in clade1.In the same calde,HvALMT1 was involved in stomatal function,which suggested that these ALMT members may play important roles in stomatal movement.（4）Real-time quantitative PCR analysis,CO₂ absorption rate and organic acid fluctuations throughout the day and night exhibited that the expression patterns of Dca N03602,Dca006649,Dca006647 and Dca006648 showed strong circadian rhythm characteristics.Dca024716 and Dca000404 were highly expressed at the junction of the photoperiod phase these results suggested that the functions of DcaALMT gene might be related to the CAM.In conclusion,these results provided comprehensive information for the study of the ALMT gene family in Dendrobium catenatum and the foundation for further functional characterization of the DcaALMT gene.