Bacterial endophytes are widespread inhabitants inside plant tissues that play crucial roles in plant growth and biotransformation. This study aimed to offer information for the exploitation of endophytes by analyzing the bacterial endophytes in different parts of Panax notoginseng. We used high-throughput sequencing methods to analyze the diversity and composition of bacterial endophytes from different parts of P. notoginseng. A total of 174,761 classified sequences were obtained from the analysis of 16S ribosomal RNA in different parts of P. notoginseng. Its fibril displayed the highest diversity of bacterial endophytes. Principal coordinate analysis revealed that the compositions of the bacterial endophytes from aboveground parts (flower, leaf, and stem) differed from that of underground parts (root and fibril). The abundances of Conexibacter, Gemmatimonas, Holophaga, Luteolibacter, Methylophilus, Prosthecobacter, and Solirubrobacter were significantly higher in the aboveground parts than in the underground parts, whereas the abundances of Bradyrhizobium, Novosphingobium, Phenylobacterium, Sphingobium, and Steroidobacter were markedly lower in the aboveground parts. Our results elucidated the comprehensive diversity and composition profiles of bacterial endophytes in different parts of 3-year-old P. notoginseng. Our data offered pivotal information to clarify the role of endophytes in the production of P. notoginseng and its important metabolites.

The aroma of peach fruit is predominantly determined by the accumulation of γ-decalactone and ester compounds. A previous study showed that the biosynthesis of these aroma compounds in peach fruit is catalyzed by PpAAT1, an alcohol acyltransferase. In this work, we investigated the key active site residues responsible for γ-decalactone and ester biosynthesis. A total of 14 candidate amino acid residues possibly involved in internal esterification and 9 candidate amino acid residues possibly involved in esterification of PpAAT1 were assessed via site-directed mutagenesis. Analyses of the in vitro enzyme activities of PpAAT1 and its site-directed mutant proteins (PpAAT1-SMs) with different amino acid residue mutations as well as the contents of γ-decalactone in transgenic tobacco leaves and peach fruits transiently expressing PpAAT1 and PpAAT1-SMs revealed that site-directed mutation of H165 in the conserved HxxxD motif led to lost enzymatic activity of PpAAT1 in both internal esterification and its reactions, whereas mutation of the key amino acid residue D376 led to the total loss of γ-decalactone biosynthesis activity of PpAAT1. Mutations of 9 and 7 other amino acid residues also dramatically affected the enzymatic activity of PpAAT1 in the internal esterification and esterification reactions, respectively. Our findings provide a biochemical foundation for the mechanical biosynthesis of γ-decalactone and ester compounds catalyzed by PpAAT1 in peach fruits, which could be used to guide the molecular breeding of new peach species with more favorable aromas for consumers.

Rational crop community structure plays an important role in maximizing the intercropping yield advantage. Effects of increasing maize densities in maize (Zea mays L.)/peanut (Arachis hypogaea L.) intercropping on yields and other agronomic traits, and the community stability of productivity were conducted across three different experimental sites. There were significant and positive correlations between maize densities and both maize grain/biomass yields and corresponding partial land equivalent ratios (LERs) across all three locations; but grain/biomass yields and partial LERs of peanut were all negatively correlated with maize densities in each or across all locations. LERs of grain yields averaged over three locations ranged from 0.89 to 0.98, while LERs of biomass yields ranged from 0.94 to 1.09 (>1.0 except for the maize inter-plant distance of 27 cm), indicating the intercropping advantage on biomass yields but not grain yields. Peanut had significantly lower kernel harvest indexes than those in monoculture. Excessive narrowing maize inter-plant distances reduced the community stability of productivity severely (especially for maize and total LERs) and are more likely to lead to abnormal maize and peanut plants. Therefore, a rational increase of maize densities in intercropping is suggested to keep the balance between maize and peanut and the comprehensive yield advantage.

Rational regulation of phosphorus (P) use in the soil–rhizosphere–plant system is challenging in the development of sustainable, intensive, and healthy agriculture. Rational maize (Zea mays L.) based intercropping with legumes/oilseed rape across six experimental sites from 2008 to 2017 proved advantageous over monoculture in terms of both maize biomass production and P uptake. The partial land equivalent ratio (PLER) for P uptake by intercropped maize averaged from 0.58 to 0.92, which was significantly higher than that for biomass production (0.51–0.78), indicating that the advantage of P acquisition by intercropped maize was superior to that of biomass accumulation. It was the excessive accumulation of P in intercropped maize compared to monoculture, especially higher P concentrations in grains that led to the superior P acquisition advantage and luxury absorption of P. P concentrations in maize grains were significantly increased from 1.89–2.91 mg kg⁻¹ in monoculture to 2.09–3.65 mg kg⁻¹, in intercropping, by 8.3%–25.5%. The plant internal P use efficiency of maize was significantly decreased from the initial 411.7–775.7 kg kg⁻¹ in monoculture to 345.7–710.4 kg kg⁻¹ in intercropping by 4.9%–16.0%, and 100 kg maize grain P quantities were significantly increased from 0.25–0.46 kg to 0.27–0.54 kg by 7.0%–17.4%. Rational fertilizer P input maximized maize yields and P use without decreasing the interspecific ecological advantages and harvest indexes of grain yields and P. These findings promoted better understanding of P allocation status within maize plants, and yield and P acquisition advantages through the exploitation of the biological potential of plants for the efficient utilization of P resources in diverse species combinations.