A reference-grade genome of the xerophyte Ammopiptanthus mongolicus sheds light on its evolution history in legumes and droughttolerance mechanisms

Plants that grow in extreme environments represent unique sources of stress-resistance genes and mechanisms.Ammopiptanthus mongolicus(Leguminosae)is a xerophytic evergreen broadleaf shrub native to semi-arid and desert regions;however,its drought-tolerance mechanisms remain poorly understood.Here,we report the assembly of a reference-grade genome for A.mongolicus,describe its evolutionary history within the legume family,and examine its drought-tolerance mechanisms.The assembled genome is 843.07 Mb in length,with 98.7%of the sequences successfully anchored to the nine chromosomes of A.mongolicus.The genome is predicted to contain 47611 protein-coding genes,and 70.71%of the genome is composed of repetitive sequences;these are dominated by transposable elements,particularly longterminal-repeat retrotransposons.Evolutionary analyses revealed two whole-genome duplication(WGD)events at 130 and 58 million years ago(mya)that are shared by the genus Ammopiptanthus and other legumes,but no species-specific WGDs were found within this genus.Ancestral genome reconstruction revealed that the A.mongolicus genome has undergone fewer rearrangements than other genomes in the legume family,confirming its status as a"relict plant".Transcriptomic analyses demonstrated that genes involved in cuticular wax biosynthesis and transport are highly expressed,both under normal conditions and in response to polyethylene glycol-induced dehydration.Significant induction of genes related to ethylene biosynthesis and signaling was also observed in leaves under dehydration stress,suggesting that enhanced ethylene response and formation of thick waxy cuticles are two major mechanisms of drought tolerance in A.mongolicus.Ectopic expression of AmERF2,an ethylene response factor unique to A.mongolicus,can markedly increase the drought tolerance of transgenic Arabidopsis thaliana plants,demonstrating the potential for application of A.mongolicus genes in crop improvement.

Pericarp and seed of litchi and longan fruits:constituent, extraction, bioactive activity, and potential utilization

Litchi(Litchi chinensis Sonn.)and longan(Dimocarpus longan Lour.)fruits have a succulent and white aril with a brown seed and are becoming popular worldwide.The two fruits have been used in traditional Chinese medicine as popular herbs in the treatment of neural pain,swelling,and cardiovascular disease.The pericarp and seed portions as the by-products of litchi and longan fruits are estimated to be approximately 30%of the dry weight of the whole fruit and are rich in bioactive constituents.In the recent years,many biological activities,such as tyrosinase inhibitory,antioxidant,anti-inflammatory,immunomodulatory,anti-glycated,and anti-cancer activities,as well as memory-increasing effects,have been reported for the litchi and longan pericarp and seed extracts,indicating a potentially significant contribution to human health.With the increasing production of litchi and longan fruits,enhanced utilization of the two fruit by-products for their inherent bioactive constituents in relation to pharmacological effects is urgently needed.This paper reviews the current advances in the extraction,processing,identification,and biological and pharmacological activities of constituents from litchi and longan by-products.Potential utilization of litchi and longan pericarps and seeds in relation to further research is also discussed.