Drought is an important abiotic factor constricting crop production globally. Although the role of JAZ proteins in regulating jasmonic acid signaling and plant responses to environmental stress is well documented, their specific functions and underlying mechanisms in plants remains little known. In this study, JAZ proteins in barley were thoroughly analyzed, revealing a total of 11 members classified into three phylogenetic subgroups. HvJAZ2, based on its distinct expression patterns, is considered as a key candidate gene for regulating drought tolerance in barley. Using the HvJAZ2 knockout mutants, we revealed that the gene negatively regulates drought tolerance by inhibiting barley root growth. Notably, the jaz2 mutants up-regulated expression of root development genes, including SHR1, PLT1, PLT2, and PLT6. plt2 and plt1/plt2 mutants exhibited suppressed root development and reduced drought tolerance. Analysis of interactions between HvJAZ2 and other proteins showed that HvJAZ2 is not directly interacted with HvPLT1/2/6, but interacts with some other proteins. BIFC and LCA assays further confirmed the nuclear interaction between HvJAZ2 and HvMYC2. Y1H and Dual-Luciferase experiments demonstrated that HvMYC2 can bind to and activates the HvPLT2 promoter. In summary, HvJAZ2 negatively regulates root development and drought tolerance in barley by suppressing HvPLT2 expression through interacting with HvMYC2.

Cadmium (Cd) contamination in the environment has becoming a hot issue worldwide, as it has posed a great risk to human health through food chain. Cd accumulation in the edible parts of crops are involved in four processes: uptake, translocation, sequestration and (re)distribution, which are all controlled by membrane transporters. In this review, the advance in studies on physiological and molecular mechanisms of Cd accumulation in plants was summarized, and then the functional evolution was discussed based on oneKP database. Cd accumulation in plants is a derived and polyphyletic trait that has evolved convergently by several times. During their evolution, the membrane transporter families, such as NRAMPs, HMAs, ABCCs, ZIPs, CDFs, CAXs and OPTs, have undergone the lineage specific expansion due to gene duplication. The orthologues of OsHMA2 in higher plants are stepwisely evolved from monophyletic evolutionary lineage with one common ancestor; whereas the orthologues of OsNRAMP5 from a polyphyletic evolutionary lineage with several ancestors. In addition, phylogenetic clusters of the orthologues of OsNRAMP5 have occurred rampant intermixing, suggesting horizontal gene transfer. It may be concluded that evolution of Cd accumulation in plants could provide an adaptive advantage for colonization of plants to the new habitats like metalliferous soil.

Cadmium (Cd) contamination in the environment has becoming a hot issue worldwide, as it has posed a great risk to human health through food chain. Cd accumulation in the edible parts of crops are involved in four processes: uptake, translocation, sequestration and (re)distribution, which are all controlled by membrane transporters. In this review, the advance in studies on physiological and molecular mechanisms of Cd accumulation in plants was summarized, and then the functional evolution was discussed based on oneKP database. Cd accumulation in plants is a derived and polyphyletic trait that has evolved convergently by several times. During their evolution, the membrane transporter families, such as NRAMPs, HMAs, ABCCs, ZIPs, CDFs, CAXs and OPTs, have undergone the lineage specific expansion due to gene duplication. The orthologues of OsHMA2 in higher plants are stepwisely evolved from monophyletic evolutionary lineage with one common ancestor; whereas the orthologues of OsNRAMP5 from a polyphyletic evolutionary lineage with several ancestors. In addition, phylogenetic clusters of the orthologues of OsNRAMP5 have occurred rampant intermixing, suggesting horizontal gene transfer. It may be concluded that evolution of Cd accumulation in plants could provide an adaptive advantage for colonization of plants to the new habitats like metalliferous soil.

Aluminum (Al) toxicity in acid soils significantly affects plant growth, agricultural productivity and ecosystem health. Here we investigated plant Al tolerance from evolutionary physiological, molecular, and ecological perspectives. Genetic similarity and phylogenetic analysis of Al tolerance-associated gene families showed that many of these were conserved from streptophyte algae to angiosperms, indicating land plants have evolved gradually in adaptation to Al-rich acid soil during plant terrestrialization. In particular, vacuolar phosphate transporter SPX-major facility superfamily (SPX-MFS) and inorganic phosphate (Pi) transporter 1 subfamily (PHT1s) of streptophyte algae showed higher genetic similarity to land plants than chlorophyte algae. PHT1 subfamily exhibited a significant expand during the evolution from streptophyte algae to liverworts and then to eudicots. Moreover, we identified an Al-tolerant Tibetan wild barley accession XZ29, showing high levels of Phosphorus(P)-containing glycolytic intermediates under Al stress. We found a new Al-tolerance mechanism that Al-induced Pi efflux from root elongation zone to chelate rhizosphere Al3+ and immobilization of Al with P reduce Al accumulation in barley root cells. These results indicated that Tibetan wild barley has evolved unique P transport and metabolism for the adaptation to harsh conditions in eastern and southeastern Tibet where acid soils contain high P.