Simple sequence repeats (SSRs) are widespread units on genome sequences, and play many important roles in plants. In order to reveal the evolution of plant genomes, we investigated the evolutionary regularities of SSRs during the evolution of plant species and the plant kingdom by analysis of twelve sequenced plant genome sequences. First, in the twelve studied plant genomes, the main SSRs were those which contain repeats of 1–3 nucleotides combination. Second, in mononucleotide SSRs, the A/T percentage gradually increased along with the evolution of plants (except for P. patens). With the increase of SSRs repeat number the percentage of A/T in C. reinhardtii had no significant change, while the percentage of A/T in terrestrial plants species gradually declined. Third, in dinucleotide SSRs, the percentage of AT/TA increased along with the evolution of plant kingdom and the repeat number increased in terrestrial plants species. This trend was more obvious in dicotyledon than monocotyledon. The percentage of CG/GC showed the opposite pattern to the AT/TA. Forth, in trinucleotide SSRs, the percentages of combinations including two or three A/T were in a rising trend along with the evolution of plant kingdom; meanwhile with the increase of SSRs repeat number in plants species, different species chose different combinations as dominant SSRs. SSRs in C. reinhardtii, P. patens, Z. mays and A. thaliana showed their specific patterns related to evolutionary position or specific changes of genome sequences. The results showed that, SSRs not only had the general pattern in the evolution of plant kingdom, but also were associated with the evolution of the specific genome sequence. The study of the evolutionary regularities of SSRs provided new insights for the analysis of the plant genome evolution.

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To characterize the differences in photosynthate distribution and transport between nitrogen(N)-tolerant and N-susceptible sweetpotato cultivars under different N conditions, three N levels, including 0 (N0), 120 (N120), and 240 kg ha−1 (N240), were used in field experiments with the Jishu26 (J26) and Xushu32 (X32) cultivars in 2015 and 2016. The results from both years revealed that high N application reduced the tuberous root yield, the tuber/vine rate of carbon-13 (13C), and top-to-base (three equal segments of stem divided from the fifth opened leaf of the shoot tip to the main stem, defined as the top, middle, and base parts, respectively) gradients such as sucrose, ammonia N and potassium along the stem. ‘J26’ showed a higher yield than ‘X32’ under N0 but lower yield than ‘X32’ under N120 and N240. It also exhibited a higher 13C distribution to tuberous roots compared with that of ‘X32’ under N0, and the opposite trend was observed under N120 and N240. Under N0, ‘J26’ showed a steep top-to-base amino acid gradient and a significantly lower top-to-base sucrose increase along the stem in the late growth stage. Under N120 and N240, ‘X32’ exhibited a greater top-to-base decrease in the ammonia N along the stem during the main growth stages, a steep top-to-base sucrose gradient along the stem in the early growth stage, and a lower top-to-base sucrose increase along the stem in the middle and late growth stages. The formation of a reasonable photosynthate distribution structure attributed to high yield was related to a desirable sucrose, ammonia N or K+ gradient downward along the stem. These results might help provide farmers with sweetpotato cultivars using less or no N fertilizer in soils of different fertility and enhance the knowledge of yield-related physiology.

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Background Sweetpotato (Ipomoea batatas (L.) Lam.) serves as an important food source for human beings. β-galactosidase (bgal) is a glycosyl hydrolase involved in cell wall modification, which plays essential roles in plant development and environmental stress adaptation. However, the function of bgal genes in sweetpotato remains unclear. Results In this study, 17 β-galactosidase genes (Ibbgal) were identified in sweetpotato, which were classified into seven subfamilies using interspecific phylogenetic and comparative analysis. The promoter regions of Ibbgals harbored several stress, hormone and light responsive cis-acting elements. Quantitative real-time PCR results displayed that Ibbgal genes had the distinct expression patterns across different tissues and varieties. Moreover, the expression profiles under various hormonal treatments, abiotic and biotic stresses were highly divergent in leaves and root. Conclusions Taken together, these findings suggested that Ibbgals might play an important role in plant development and stress responses, which provided evidences for further study of bgal function and sweetpotato breeding.

Background: Sweet potato (Ipomoea batatas (L.) Lam.) is a highly heterozygous autohexaploid crop with high yield and high anthocyanin content. Purple sweet potato is the main source of anthocyanins, and the mechanism of anthocyanin biosynthesis in storage roots has not been fully revealed. Results: In order to reveal the mechanism of anthocyanin biosynthesis and identify new homologous genes involved in anthocyanin biosynthesis in the storage roots of sweet potato, we used Ningzishu 1 and Jizishu 2 as parents to construct a F 1 hybrid population. Seven anthocyanin-containing lines and three anthocyanin-free lines were selected for full-length and second-generation transcriptome analyses. A total of 598,375 circular consensus sequencing reads were identified from full-length transcriptome sequencing. After analysis and correction of second-generation transcriptome data, 41,356 transcripts and 18,176 unigenes were obtained. Through a comparative analysis between anthocyanin-containing and anthocyanin-free groups 2329 unigenes were found to be significantly differentially expressed, of which 1235 were significantly up-regulated and 1094 were significantly down-regulated. GO enrichment analysis showed that the differentially expressed unigenes were significantly enriched in molecular function and biological process. KEGG enrichment analysis showed that the up-regulated unigenes were significantly enriched in the flavonoid biosynthesis and phenylpropanoid biosynthesis pathways, and the down-regulated unigenes were significantly enriched in the plant hormone signal transduction pathway. Weighted gene co-expression network analysis of differentially expressed unigenes revealed that anthocyanin biosynthesis genes were co-expressed with transcription factors such as MYB, bHLH and WRKY at the transcription level.