microRNAs(miR NAs) are important post-transcriptional regulators of gene expression in plant abiotic stress responses. Ammopiptanthus mongolicus is a typical evergreen woody xerophyte, which makes it an ideal model system for studying drought tolerance in woody plants. The response of mi RNAs to drought stress is still unknown in this plant. In this research, we obtained 34 695 665 raw reads from two small RNA libraries constructed from control and drought-treated A. mongolicus seedlings by the Illumina deep sequencing technology. Length analysis revealed that reads of 20, 21, and 24 nucleotides accounted for the majority of the small RNAs in the two libraries. Sequence analyses identified 65 conserved mi RNA sequences from 190 members of 31 mi RNA families and 20 potential novel mi RNAs from 17 families that were differentially expressed between the two libraries. The expression patterns of 25 of these mi RNAs were significantly different in the two libraries, but only am-mi R4 a-c was downregulated during drought stress, the other 24 were upregulated. The expression trends determined by the Hi Seq sequencing and by q RT-PCR were similar. Furthermore, 35 target genes for the conserved mi RNA were markedly changed and 52 target genes for the potential novel mi RNAs were predicted and their functions were annotated by computational analysis. Our results provide new molecular evidence for understanding the molecular mechanisms of drought response and tolerance in A. mongolicus.
LIU ShengliNI YanjieHE QianWANG JinyuCHEN YuzhenLU Cunfu
Aim Mirabilis himalaica(Nyctaginaceae)is an endangered medicinal plant mainly distributed in the plateau region of northern Tibet,China.The outer surface of M.himalaica achenes is covered by a pectinaceous mucilaginous layer upon hydration.However,the role of the achene mucilage is poorly understood.in this study,we inves-tigated the effects of mucilage on achene germination and sprout growth under abiotic stress to explain how M.himalaica survive the alpine environment.Methods We investigated the effect of mucilage on achenes germination by contrast the capacity of water absorption,dehydration and respira-tion of intact achene and the achene with mucilage removal.We performed abiotic stresses experiments including drought stress,salt stress,cold stress and high temperature stress,and quantified the effects of mucilage removal on achene germination rate,root and shoot lengths of seedlings.Important Findings Mucilage is extremely hydrophilic,and the mass of intact achenes can be 9-fold greater than that of demucilaged achenes.The removal of the mucilaginous layer did not significantly change final germination percentages under ideal conditions,but intact achenes(i.e.with muci-lage)took longer to germinate.The mucilage significantly decreased seed respiration rates by acting as a physical barrier that prevented oxygen diffusion.Germination rates,shoot and root growth of intact achenes were higher than those of demucilaged ones during exposures to cold,heat,osmotic and salt stresses.Achene mucilage presumably plays an ecologically important role in the life cycle of M.himalaica by aiding the critical achene germination and early seedling growth in the stressful habitats of the plateau region of northern Tibet.
Yuzhen ChenLu ZhangXiao LuXiaozhong LanMan ShenCunfu Lu
Trees in temperate regions exhibit evident seasonal patterns,which play vital roles in their growth and development.The activity of cambial stem cells is the basis for regulating the quantity and quality of wood,which has received considerable attention.However,the underlying mechanisms of these processes have not been fully elucidated.Here we performed a comprehensive analysis of morphological observations,transcriptome profiles,the DNA methylome,and miRNAs of the cambium in Populus tomentosa during the transition from dormancy to activation.Anatomical analysis showed that the active cambial zone exhibited a significant increase in the width and number of cell layers compared with those of the dormant and reactivating cambium.Furthermore,we found that differentially expressed genes associated with vascular development were mainly involved in plant hormone signal transduction,cell division and expansion,and cell wall biosynthesis.In addition,we identified 235 known miRNAs and 125 novel miRNAs.Differentially expressed miRNAs and target genes showed stronger negative correlations than other miRNA/target pairs.Moreover,global methylation and transcription analysis revealed that CG gene body methylation was positively correlated with gene expression,whereas CHG exhibited the opposite trend in the downstream region.Most importantly,we observed that the number of CHH differentially methylated region(DMR)changes was the greatest during cambium periodicity.Intriguingly,the genes with hypomethylated CHH DMRs in the promoter were involved in plant hormone signal transduction,phenylpropanoid biosynthesis,and plant–pathogen interactions during vascular cambium development.These findings improve our systems-level understanding of the epigenomic diversity that exists in the annual growth cycle of trees.
Bo ChenHuimin XuYayu GuoPaul GrunhoferLukas SchreiberJinxing LinRuili Li
Microsporogenesis and flower development in Eucalyptus urophylla 9 E. grandis were examined using chromosome tableting to provide a method to predict the meiotic stages in this species. Although microsporogenesis was normal, cytokinesis during meiosis of pollen mother cells occurred simultaneously, with strong asynchronism observed in the two different lengths of stamens in a flower bud. In a single flower, the developmental period of microsporogenesis in anthers on the longer stamens was always ahead of those on the shorter stamens. Flower development was also asynchronous at different locations on a branch. Flower buds on the upper side of the branch were larger in diameter than those on the lower side. In addition,a correlation was observed between microsporogenesisdevelopment and flower bud diameter growth. The pachytene stage was first observed when the diameter of the flower buds increased to 3.0 mm, and the majority of the meiotic stages were observed when bud diameters ranged from 3.5 to5.0 mm. This study showed that the developmental stages of microsporogenesis in Eucalyptus urophylla 9 E. grandis could be distinguished readily, which may be applicable to future breeding studies.
Jun YangJun LanPengqiang YaoZhen HuangXiangyang Kang
The plant cytoskeleton undergoes dynamic remodeling in response to diverse developmental and environmental cues. Remodeling of the cytoskeleton coordinates growth in plant cells, including trafficking and exocytosis of membrane and wall components during cell expansion, and regulation of hypocotyl elongation in response to light. Cytoskeletal remodeling also has key functions in disease resistance and abiotic stress responses. Many stimuli result in altered activity of cytoskeleton-associatedproteins,microtubuleassociated proteins(MAPs) and actin-binding proteins(ABPs). MAPs and ABPs are the main players determining the spatiotemporally dynamic nature of the cytoskeleton, functioning in a sensory hub that decodes signals to modulate plant cytoskeletal behavior. Moreover, MAP and ABP activities and levels are precisely regulated during development and environmental responses, but our understanding of this process remains limited. In this review, we summarize the evidence linking multiple signaling pathways, MAP and ABP activities and levels, and cytoskeletal rearrangements in plant cells. We highlight advances in elucidating the multiple mechanisms that regulate MAP and ABP activities and levels, including calcium and calmodulin signaling, ROP GTPase activity, phospholipid signaling, and post-translational modifications.
