Structure and expression profile of the sucrose synthase gene family in the rubber tree: indicative of roles in stress response and sucrose utilization in the laticifers

Abstract

Sucrose synthase (Sus, http://www.chem.qmul.ac.uk/iubmb/enzyme/EC2/4/1/13.html) is widely recognized as a key enzyme in sucrose metabolism in plants. However, nothing is known about this gene family in Hevea brasiliensis (para rubber tree). Here, we identified six Sus genes in H. brasiliensis that comprise the entire Sus family in this species. Analysis of the gene structure and phylogeny of the Sus genes demonstrates evolutionary conservation in the Sus families across Hevea and other plant species. The expression of Sus genes was investigated via Solexa sequencing and quantitative PCR in various tissues, at various phases of leaf development, and under abiotic stresses and ethylene treatment. The Sus genes exhibited distinct but partially redundant expression profiles. Each tissue has one abundant Sus isoform, with HbSus3, 4 and 5 being the predominant isoforms in latex (cytoplasm of rubber‐producing laticifers), bark and root, respectively. HbSus1 and 6 were barely expressed in any tissue examined. In mature leaves (source), all HbSus genes were expressed at low levels, but HbSus3 and 4 were abundantly expressed in immature leaves (sink). Low temperature and drought treatments conspicuously induced HbSus5 expression in root and leaf, suggesting a role in stress responses. HbSus2 and 3 transcripts were decreased by ethylene treatment, consistent with the reduced sucrose‐synthesizing activity of Sus enzymes in the latex in response to ethylene stimulation. Our results are beneficial to further determination of functions for the Sus genes in Hevea trees, especially roles in regulating latex regeneration.

The calcium‐dependent protein kinase (CDPK) and CDPK‐related kinase gene families in Hevea brasiliensis—comparison with five other plant species in structure, evolution, and expression

“…6, the results from sequencing‐based expression analyses were broadly similar to the qPCR results at least one time point post treatment. The RNA‐seq data were also verified by our published analyses 38, 49. Above all, we can verify that the results of the RNA‐seq analyses on HbCPK genes are authentic.…”

Genome-Wide Identification and Expression Profile Analysis of Citrus Sucrose Synthase Genes: Investigation of Possible Roles in the Regulation of Sugar Accumulation

“…Similar with A. thaliana [11], O. sativa [12], G. arboreum [13] and H. brasiliensis [8], we discovered that there are also at least six Sus gene members in the citrus genome (Table 2) by searching sweet orange and Clementine genomic databases and with PCR amplification. Similarity analysis of the partially cloned CitSus 1-6 from C. unshiu fruits showed the highest identity (over 98%) with the genomic sequence (Table S1) and batch CD-search indicated that they also have two typically conserved domains of Sus polypeptide (GT1_Sucrose_Synthase and Glycosyltransferase_GTB_type superfamily) (Table S4), which confirmed their authenticity in the citrus genome.…”

“…Of them, Sus catalyzes the reversible reaction of sucrose and UDP into UDP-glucose and fructose, whereas Inv hydrolyzes sucrose into glucose and fructose [2]. It is known that Sus plays pivotal roles in a variety of plant metabolic processes, such as sucrose distribution in plant tissues [3], [4], [5], [6], starch biosynthesis, cellulose synthesis and secondary cell-wall formation [7], response to abiotic stresses [3], [5], [8] and nitrogen fixation [9]. In citrus, Sus has shown its potential roles in fruit development and in promoting sugar accumulation in the juice sacs (JS) of grapefruit ( Citrus paradisi ) [10].…”

“…It is known that Sus isoforms are encoded by a small multi-gene family. For instance, the Sus family is comprised of six distinct members in the model plant Arabidopsis thaliana [11], Oryza sativa [12], Gossypium arboreum [13] and Hevea brasiliensis [8]. In addition, four Sus genes were found in Hordeum vulgare [14], whereas seven Sus genes were found in the genus Populus [15], [16].…”

“…Although three Sus genes ( CuSuSy 1, CuSuSy 2 and CuSuSyA ) were isolated from C. unshiu fruits by PCR, using a shuttle method a decade before [20], it was predicted that there would be more Sus genes in the citrus genome due to the number of Sus genes reported in other plants [8], [11], [12], [13]. Because citrus genome sequences have been published (http://citrus.hzau.edu.cn/orange/ and http://www.phytozome.net/), it is possible to identify more citrus Sus genes.…”