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Guar (Cyamopsis tetragonoloba), a short-day annual legume plant, is an economically important industrial crop with richness in high valuable guar gum. The photoperiod limits guar's cultivated region, however, the mechanism of photoperiod effects on guar remains ambiguous. Based on Illumina RNA-seq, PacBio Iso-seq and UPLC-MS for analysis, the current study used different photoperiods to cultivate guar to illustrate the mechanism. The results showed that numerous genes responded to photoperiods differentially, involved in rhythm, flowering, biosynthesis and metabolism pathways. As processing time increased, the number of differentially expressed genes (DEGs) increased from 2518 to 5708. The genes of rhythm, flowering and key transcription factors phyA , GI, ELF3 , TOC1 , NF-Y and GATA positively responded to short-day, Whereas PRR , FLC , SVP , COL16 and B3 responded negatively to short-day, but positively to long-day. Additionally, the long-day inhibited the expression of genes related to phytohormones metabolism, such as GA synthetic correlation genes GA20ox and GA3ox , and JA synthesis genes AOS and ACX. As a result, the levels of GA and JA reduced, indicating their essential regulatory function in guar flowering. Furthermore, the expressions of the galactomannan synthesis genes were not influenced by photoperiod. In short, the phyA , GI, ELF3 , TOC1 , NF-Y , GATA, GA20ox and GA3ox were selected as candidate genes for flowering-promotion, while the PRR , FLC , SVP , COL16 and B3 for flowering-repression. This study provides several vital candidate genes for further genetic improvement for obtaining insensitive guar to photoperiod. • Reported mechanisms for the photoperiodic response in guar. • Revealed genes responsible for inhibition of guar flowering. • Provided insights for further breeding stable gum yield guar variety adapted to long-day or insensitive to photoperiod. • Constructed the first guar reference transcript dataset by third-generation transcriptome. [ABSTRACT FROM AUTHOR]

Cyamopsis tetragonoloba (L.), an annual leguminous crop, with wide and important industrial applications. Its seeds contain large amounts of guar gum, main ingredient is galactomannan, have multiple application values. To reveal the genome resource of guar, this study describes the assembly of C. tetragonoloba chromosome-level genome CteV1.0. There were 18.35 Gb high accuracy HiFi data with the more than 40× sequencing depth were generated by the PacBio platform with average length 22.61 kb. Finally, the assembled size of C. tetragonoloba genome was 482.45 Mb with a 62.64 Mb scaffold N50. Then with Hi-C assembly and adjustment, the 99.07% (477.96 Mb/482.45 Mb) of genome data was assigned to 7 pseudochromosomes. A total of 31,251 genes (31251/31867, 98.07%) were successfully annotated, and 309 gene families contracted, 559 gene families expanded in C. tetragonoloba. This genome of guar provides fundamental biological information of the industrial benefits, biophysiological functions and unique evolutionary relationship. The comparison between guar and other related short-day and long-day species characterized the photoperiodic differences in genomic scale. The construction of genome assembly, gene function and photoperiod adaption in C. tetragonoloba may reveal the basic theoretical fundament of the special traits in C. tetragonoloba. This available high-quality genomic resource in this study will facilitate future research in guar field. [Display omitted] • The first available chromosome-level guar reference genome. • Genome size 482.45 Mb, scaffold N50 62.64 Mb, LAI 11.09, BUSCO score 98.45%, CEGMA score 99.34%. • Guar is similar to short-day leguminous species in gene families and gene copy. [ABSTRACT FROM AUTHOR]