Water Deficit Transcriptomic Responses Differ in the Invasive Tamarix chinensis and T. ramosissima Established in the Southern and Northern United States.

Padmapriya Swaminathan,Michelle Ohrtman,John Gaskin,Anup Deuja,Cankun Wang,Anne Fennell,Sharon Clay,Abigail Carinder

doi:10.3390/plants9010086

Abstract

Tamarix spp. (saltcedar) were introduced from Asia to the southern United States as windbreak and ornamental plants and have spread into natural areas. This study determined differential gene expression responses to water deficit (WD) in seedlings of T. chinensis and T. ramosissima from established invasive stands in New Mexico and Montana, respectively. A reference de novo transcriptome was developed using RNA sequences from WD and well-watered samples. Blast2GO analysis of the resulting 271,872 transcripts yielded 89,389 homologs. The reference Tamarix (Tamaricaceae, Carophyllales order) transcriptome showed homology with 14,247 predicted genes of the Beta vulgaris subsp. vulgaris (Amaranthaceae, Carophyllales order) genome assembly. T. ramosissima took longer to show water stress symptoms than T. chinensis. There were 2068 and 669 differentially expressed genes (DEG) in T. chinensis and T. ramosissima, respectively; 332 were DEG in common between the two species. Network analysis showed large biological process networks of similar gene content for each of the species under water deficit. Two distinct molecular function gene ontology networks (binding and transcription factor-related) encompassing multiple up-regulated transcription factors (MYB, NAC, and WRKY) and a cellular components network containing many down-regulated photosynthesis-related genes were identified in T. chinensis, in contrast to one small molecular function network in T. ramosissima.

Highlights

Tamarix, tamarisk, or saltcedar (T. chinensis, T. ramosissima, other Tamarix species, and hybrids) is an exotic shrub/tree that is the second most abundant riparian woody plant in the western UnitedStates [1]
Transcriptome analysis for the 1440 benchmarking universal single-copy orthologs (BUSCO), which provides a quantitative assessment of an assembly [39], indicated that 92% of the BUSCO genes were present (419 complete and single copy genes, 777 complete and duplicated genes, and 132 fragmented genes)
T. chinensis introduction in the 19th century and other species in the 20th century [2], Tamarix species and hybrids extend from the southwest to the north-central region

Summary

Introduction

Tamarisk, or saltcedar (T. chinensis, T. ramosissima, other Tamarix species, and hybrids) is an exotic shrub/tree that is the second most abundant riparian woody plant in the western UnitedStates [1]. Tamarisk, or saltcedar (T. chinensis, T. ramosissima, other Tamarix species, and hybrids) is an exotic shrub/tree that is the second most abundant riparian woody plant in the western United. Multiple introductions of Tamarix species were planted across the southwestern United. States for erosion control and windbreak purposes [2]. This has led to hybridization, resulting in multiple complexes, rather than individual species, becoming the dominant Tamarix taxa in North. T. chinensis and T. ramosissima are the most common invasive Tamarix in the United States. Extensive hybridization of these two species is found in North America, with hybrid genotypes extending from

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