Sucrose Unloading Pathway And Gene Expression Analysis Of Sugar Metabolism And Transportation In Bamboo Shoots Of Bambusa Emeiensis

The reasonable distribution and efficient utilization of plant photosynthesis products are of great significance for increasing plant biomass and energy crisis.Bambusa emeiensis is an important economical bamboo species,but it’s not clear that the mechanism of carbohydrate operation,metabolism and distribution during the growth process of Bambusa emeiensis.In this study,using transcriptome database information of different developmental stages of Bambusa emeiensis shoots,combined with phloroglucinol and safranine staining,CFDA fluorescence tracing and transmission electron microscopy,the transportation and distribution of photosynthate and the expression of related genes were analyzed.The main results were as follows:（1）During the early growth of the bamboo shoots,the soluble invertase（INV）and sucrose synthase（SUS）in the first internode at the base of the bamboo shoots play an important role in catalyze the decomposition of sucrose into hexose.Especially,the hexose decomposed by SUS was mainly used for the synthesis of compounds such as starch and cellulose,and provides energy support for the rapid growth of bamboo shoots.（2）Based on the annotations of the Bambusa emeiensis transcriptome database,combined with the known gene sequence information from rice and maize,55 sucrose hydrolyzed protein-related and 56 sugar transporter-related unigenes were identified.（3）CFDA fluorescence tracer found that the fluorescence was limited in the vascular bundles of the bamboo shoots,and failed to further diffuse out of the vascular bundle sheaths with thickened lignified walls.The symplast pathway was blocked in the connection between the phloem and the surrounding parenchyma cells to form a symptom isolation.Transmission electron microscopy observation of the ultrastructure of the bamboo shoots revealed that there were plasmodesmata between the sieve tubes,companion cells and parenchyma cells in the vascular bundle,which further confirmed the results of CFDA fluorescence tracing.（4）The results of safranin staining and tissue localization of soluble invertase indicated that the thickened vascular bundle sheath of the lignified wall failed to form a barrier to the apoplast pathway.（5）The effects of dark treatment on the apoplastic unloding pathway of vascular bundle were analyzed.The results showed that dark treatment significantly activated the expression of SUS and CWINV genes,and sugar transport related genes such as SUT and STP in the lateral branches of Bambusa emeiensis,but the expression of efflux genes SWEET and sucrose synthesis-related SPS gene was down-regulated.