Genome-wide identification and expression analysis of the BZR gene family in Zanthoxylum armatum DC and functional analysis of ZaBZR1 in drought tolerance.

MAIN CONCLUSION: In this study, six ZaBZRs were identified in Zanthoxylum armatum DC, and all the ZaBZRs were upregulated by abscisic acid (ABA) and drought. Overexpression of ZaBZR1 enhanced the drought tolerance of transgenic Nicotiana benthamian. Brassinosteroids (BRs) are a pivotal class of sterol hormones in plants that play a crucial role in plant growth and development. BZR (brassinazole resistant) is a crucial transcription factor in the signal transduction pathway of BRs. However, the BZR gene family members have not yet been identified in Zanthoxylum armatum DC. In this study, six members of the ZaBZR family were identified by bioinformatic methods. All six ZaBZRs exhibited multiple phosphorylation sites. Phylogenetic and collinearity analyses revealed a closest relationship between ZaBZRs and ZbBZRs located on the B subgenomes. Expression analysis revealed tissue-specific expression patterns of ZaBZRs in Z. armatum, and their promoter regions contained cis-acting elements associated with hormone response and stress induction. Additionally, all six ZaBZRs showed upregulation upon treatment after abscisic acid (ABA) and polyethylene glycol (PEG), indicating their participation in drought response. Subsequently, we conducted an extensive investigation of ZaBZR1. ZaBZR1 showed the highest expression in the root, followed by the stem and terminal bud. Subcellular localization analysis revealed that ZaBZR1 is present in the cytoplasm and nucleus. Overexpression of ZaBZR1 in transgenic Nicotiana benthamiana improved seed germination rate and root growth under drought conditions, reducing water loss rates compared to wild-type plants. Furthermore, ZaBZR1 increased proline content (PRO) and decreased malondialdehyde content (MDA), indicating improved tolerance to drought-induced oxidative stress. The transgenic plants also showed a reduced accumulation of reactive oxygen species. Importantly, ZaBZR1 up-regulated the expression of drought-related genes such as NbP5CS1, NbDREB2A, and NbWRKY44. These findings highlight the potential of ZaBZR1 as a candidate gene for enhancing drought resistance in transgenic N. benthamiana and provide insight into the function of ZaBZRs in Z. armatum.

Small RNA sequencing provides candidate miRNA-target pairs for revealing the mechanism of apomixis in Zanthoxylum bungeanum.

BACKGROUND: Apomixis is a form of asexual reproduction that produces offspring without the need for combining male and female gametes, and the offspring have the same genetic makeup as the mother. Therefore, apomixis technology has great application potential in plant breeding. To identify the apomixis types and critical period, embryonic development at different flower development stages of Zanthoxylum bungeanum was observed by cytology. RESULTS: The results show that the S3 stage is the critical period of apomixis, during which the nucellar cells develop into an adventitious primordial embryo. Cytological observations showed that the type of apomixis in Z. bungeanum is sporophytic apomixis. Furthermore, miRNA sequencing, miRNA-target gene interaction, dual luciferase reporter assay, and RT-qPCR verification were used to reveal the dynamic regulation of miRNA-target pairs in Z. bungeanum apomixis. The miRNA sequencing identified 96 mature miRNAs, of which 40 were known and 56 were novel. Additionally, 29 differentially expressed miRNAs were screened according to the miRNAs expression levels at the different developmental stages. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analyses showed that the target genes of the differentially expressed miRNAs were mainly enriched in plant hormone signal transduction, RNA biosynthetic process, and response to hormone pathways. CONCLUSIONS: During the critical period of apomictic embryonic development, miR172c significantly reduces the expression levels of TOE3 and APETALA 2 (AP2) genes, thereby upregulating the expression of the AGAMOUS gene. A molecular regulation model of miRNA-target pairs was constructed based on their interactions and expression patterns to further understand the role of miRNA-target pairs in apomixis. Our data suggest that miR172c may regulates AGAMOUS expression by inhibiting TOE3 in the critical period of apomixis.

Long-term persistence of pioneer species in tropical rain forest soil seed banks.

In tropical forests, pioneer tree species regenerate from seeds dispersed directly into canopy gaps and from seeds that persisted in soil seed banks before gap formation. Life-history models have suggested that selection for the long-term persistence of tree seeds in the soil should be weak because persistence potentially reduces population growth rate by extending generation time and because adult life spans may exceed the return interval of favorable recruitment sites. Here we use accelerator mass spectrometry to carbon-date seeds of three pioneer tree species extracted from undisturbed seed banks in seasonally moist lowland Neotropical forest. We show that seeds of Croton billbergianus, Trema micrantha, and Zanthoxylum ekmannii germinate successfully from surface soil microsites after 38, 31, and 18 years, respectively. Decades-long persistence may be common in large-seeded tropical pioneers and appears to be unrelated to specific regeneration requirements.

Legume plants may facilitate Zanthoxylum bungeanum tolerance to extreme rainfall.

A complete randomized design was implemented with two watering regimes (extreme rainfall and control) and three different plant combinations (Zanthoxylum bungeanum, Z. bungeanum + Capsicum annum, Z. bungeanum + Glycine max) in order to assess the morphological and physio-biochemical responses of focal and neighbor plants. The results indicated that, extreme rainfall had significantly negative impacts on Z. bungeanum in three intercropping systems. However, intercropping with G. max improved the transpiration rate (Tr) and stomatal conductance (Gs), raised leaf relative water content (LRWC), increased chlorophyll a (Chl a) and carotenoid (Car) content, and enhanced the superoxide dismutase activity (SOD) of Z. bungeanum. After recovery, the Z. bungeanum + G. max mixed culture significantly increased soil NO3--N, improved the intercellular carbon dioxide concentration (Ci) and Tr, upregulated soluble sugar and proline, and enhanced hydrogen peroxidase activity (CAT). Moreover, the higher root biomass of G. max provided much more nitrogen for Z. bungeanum via the return of organic matter. However, intercropping with C. annum significantly increased active oxygen (ROS). Compared with neighboring species, in intercropping systems, G. max could have improved the tolerance of the focal species Z. bungeanum in response to extreme rainfall and its recovery after extreme rainfall.

Fire effects on the population structure of Zanthoxylum rhoifolium Lam (Rutaceae) in a Brazilian savanna.

Since cerrado fires may impede the growth of seedlings into trees, they may shape the population of woody species. In this study, we assessed the effects of a severe fire on the population structure and spatial distribution of Zanthoxylum rhoifolium, a widespread cerrado tree. We were interested to know the importance of the resprouting and sexual reproduction in regenerating the population. The study area had been for about six years protected from fire, before a severe fire at the end of the dry season in 2006. We sampled and measured all individuals of Z. rhoifolium found in 80 plots of 25 m(2). We found 149 individuals before the fire and 112 after the fire, of which 77 were resprouts from burned seedlings and saplings. We did not find significant differences between the population structure before and after the fire. The spatial distribution of the population remained clumped after the fire. Thus, the Z. rhoifolium population was very resilient to a severe fire. We did not find any new seedlings. As a consequence, resprouting seems to be more important than sexual reproduction in promptly regenerating the Z. rhoifolium populations.

Fire effects on the population structure of Zanthoxylum rhoifolium Lam (Rutaceae) in a Brazilian savanna / Efeitos do fogo na estrutura da população de Zanthoxylum rhoifolium Lam (Rutaceae) em uma savana brasileira

Since cerrado fires may impede the growth of seedlings into trees, they may shape the population of woody species. In this study, we assessed the effects of a severe fire on the population structure and spatial distribution of Zanthoxylum rhoifolium, a widespread cerrado tree. We were interested to know the importance of the resprouting and sexual reproduction in regenerating the population. The study area had been for about six years protected from fire, before a severe fire at the end of the dry season in 2006. We sampled and measured all individuals of Z. rhoifolium found in 80 plots of 25 m². We found 149 individuals before the fire and 112 after the fire, of which 77 were resprouts from burned seedlings and saplings. We did not find significant differences between the population structure before and after the fire. The spatial distribution of the population remained clumped after the fire. Thus, the Z. rhoifolium population was very resilient to a severe fire. We did not find any new seedlings. As a consequence, resprouting seems to be more important than sexual reproduction in promptly regenerating the Z. rhoifolium populations.

Uma vez que as queimadas no cerrado podem impedir o crescimento de plântulas, elas podem moldar a população de espécies arbóreas. Neste estudo, avaliamos os efeitos de uma queimada severa na estrutura e na distribuição espacial da população de Zanthoxylum rhoifolium, uma espécie de árvore comum no cerrado. O objetivo era saber a importância relativa do rebrotamento e da reprodução sexuada na regeneração da população. A área de estudo, há aproximadamente seis anos sem queimar, sofreu uma queimada severa no final da estação seca de 2006. Amostramos todos os indivíduos de Z. rhoifolium encontrados em 80 parcelas de 25 m². Encontramos 149 indivíduos antes do fogo e 112 depois dele, dos quais 77 eram rebrotas de plântulas e jovens queimados. Não encontramos diferenças significativas entre a estrutura da população antes e após o fogo. A distribuição espacial da população permaneceu agregada após a queimada. Portanto, a população de Z. rhoifolium foi resiliente ao fogo. Não foi encontrada nenhuma nova plântula. Consequentemente, o rebrotamento parece ser mais importante que a reprodução sexuada na regeneração imediata das populações de Z. rhoifolium.