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In this study, micro computed tomography (Micro-CT) was employed to scan the leaf buds of walnut, and 898 scanning pictures with a total of 3.4 GB were obtained. The shape, size, external characteristics and internal structure of walnut leaf buds were clearly displayed by reconstructing the 3D virtual leaf buds based on the scanning images. Our results showed that the structure of the leaf bud, in successive order from outside to inside, was composed of squamae, young leaves and vascular bundles, and there were 8 bud scales and 5 young leaves for each leaf bud. The results suggested that this technology would provide an effective way for the realization of 3D visualization of walnut leaf bud, and the video production of virtual observation of fruit tree leaf bud, as well as the construction of digital leaf bud.

FLOWERING LOCUS T (FT) is an important integrator of flowering genetic pathways and plays crucial roles in flowering transition. The tea-oil tree (Camellia oleifera Abel.) is a valuable woody oil crop, but the molecular mechanisms controlling flowering are still unclear. In this study, a FT-like gene, CoFT1, was isolated and characterized from C. oleifera. The CoFT1 protein was localized in the nucleus and cytoplasm of Arabidopsis protoplasts, and exhibited no transactivation activity in yeast cells. CoFT1 was highly expressed in mature leaves and reproductive organs, such as flower buds, flowers, flower organs, and young fruits. Its expression showed diurnal rhythms under both long-day and short-day conditions, and was photoperiod-dependent. Seasonal expression analysis revealed that the CoFT1 transcript in leaves increased during the floral induction period. Overexpression of CoFT1 in wild-type Arabidopsis resulted in precocious flowering and elevated the transcription levels of flowering related genes, such as SOC1, AP1, and LFY. Furthermore, the yeast two-hybrid and bimolecular fluorescence complementation assays demonstrated that CoFT1 was able to interact with both Arabidopsis FD and C. oleifera CoFD proteins. The sequence analysis revealed that the CoFT1 promoter contained a number of light-responsive elements, several hormonal- and stress-responsive motifs, and flowering related transcriptional factor binding sites, including CORE, CCAATBOX1, and CArG motifs. Our results suggested that CoFT1 might function as a flowering promoter in C. oleifera.

The role of polyol transporters in stress tolerance in plants have been elucidated by many studies. Sorbitol transporter genes MdSOT3, MdSOT4 and MdSOT5 in apple plants, which are important for sorbitol loading and unloading, are regulated by drought stress. To further confirm the role of sorbitol transporters in stress tolerance, the constructs harboring MdSOT3 and MdSOT5 genes were introduced into wild type Arabidopsis plants (Col-0) and the Arabidopsis transformed with MdSOT3 or MdSOT5 performed higher drought stress tolerance compared to WT. In order to further understand how sorbitol transporters are involved in drought tolerance in apple plants, upstream regions of sorbitol transporter genes were isolated from apple plant source leaves by Anchored PCR from genomic DNA obtained, and then were used to drive expression of the GUS reporter in tobacco plants. The results showed that the longest fragments of MdSOT3 and MdSOT5 promoters induced the highest GUS activity under drought stress conditions. Additionally, fragments of these promoters that contain cis-acting elements known to be involved in stress response also induced GUS activity under drought stress. Taken together, our data suggest that increased MdSOT3 and MdSOT5 activity, through cis-acting elements in the promoters of these genes, play important roles in imparting tolerance to drought in micropropagated apple plants.

A LEAFY/FLORICAULA (LFY/FLO) homolog PpLFL (PrunuspersicaLEAFY/FLORICAULALike) gene was isolated from axillary buds of peach (Prunus persica (L.) Batsch. cv. Bayuecui) during flower induction period. The open reading frame of PpLFL spanned 1,248 bp, encoding a putative protein of 415 amino acid residues, which was with high similarity (50.48 %–84.69 %) to other FLO/LFY inferred proteins from different species. The spatial expression patterns of PpLFL were detected in axillary buds during the periods of flower induction by using immunohistolocalisation. The results showed that PpLFL gene was mainly expressed during flower induction time, and also in leaf and petal promordia at the SAM. For further functional analysis, the PpLFL was constitutively expressed in the Arabidopsis lfy mutant background, and the results showed that overexpression of PpLFL under the control of CaMV 35S promoter can accelerate flowering and give rise to normal flower organs. Our results suggest that PpLFL might play an important role in flower induction, and could act as a functional flower meristem identity gene in peach.

Background Auxin plays important roles in hormone crosstalk and the plant’s stress response. The auxin-responsive Gretchen Hagen3 (GH3) gene family maintains hormonal homeostasis by conjugating excess indole-3-acetic acid (IAA), salicylic acid (SA), and jasmonic acids (JAs) to amino acids during hormone- and stress-related signaling pathways. With the sequencing of the apple (Malus × domestica) genome completed, it is possible to carry out genomic studies on GH3 genes to indentify candidates with roles in abiotic/biotic stress responses. Results Malus sieversii Roem., an apple rootstock with strong drought tolerance and the ancestral species of cultivated apple species, was used as the experimental material. Following genome-wide computational and experimental identification of MdGH3 genes, we showed that MdGH3s were differentially expressed in the leaves and roots of M. sieversii and that some of these genes were significantly induced after various phytohormone and abiotic stress treatments. Given the role of GH3 in the negative feedback regulation of free IAA concentration, we examined whether phytohormones and abiotic stresses could alter the endogenous auxin level. By analyzing the GUS activity of DR5::GUS-transformed Arabidopsis seedlings, we showed that ABA, SA, salt, and cold treatments suppressed the auxin response. These findings suggest that other phytohormones and abiotic stress factors might alter endogenous auxin levels. Conclusion Previous studies showed that GH3 genes regulate hormonal homeostasis. Our study indicated that some GH3 genes were significantly induced in M. sieversii after various phytohormone and abiotic stress treatments, and that ABA, SA, salt, and cold treatments reduce the endogenous level of axuin. Taken together, this study provides evidence that GH3 genes play important roles in the crosstalk between auxin, other phytohormones, and the abiotic stress response by maintaining auxin homeostasis.