Protophloem and metaphloem sieve tubes are essential for transporting carbohydrates and signalling molecules towards sink tissues. OCTOPUS (OPS) was previously identified as an important regulator of protophloem differentiation in Arabidopsis roots. Here, we investigated the role of OCTOPUS-LIKE 2 (OPL2), a gene homologous to OPS. OPL2 expression patterns were analysed, and functional equivalence of OPS and OPL2 was tested. Mutant and double mutant phenotypes were investigated. OPS and OPL2 displayed overlapping expression patterns and a high degree of functional overlap. A mutation in OPL2 revealed redundant functions of OPS and OPL2 in developmental processes in which OPS was known to play a role, notably cotyledon vascular patterning and protophloem development. Moreover, we also uncovered redundant roles for OPS and OPL2 in leaf vascular patterning and, most interestingly, metaphloem sieve tube differentiation. Our results reveal a novel OPS-like protein that, together with OPS, is an important regulator of vascular patterning, root growth and phloem development. OPS and OPL2 are the first genes identified that play a role in metaphloem sieve tube differentiation.

Strategy to control an invasive neophyte: the study case of kudzu Kudzu (Pueraria lobata) is a vine native to East Asia that grows under optimal conditions up to 30 cm per day. In Switzerland, the species is found on the blacklist of the invasive neophytes. At present 41 spots covering 35 141 m2 are known in southern Switzerland. Historical spots known since 2006 have extended their area by 45% in the last six years, whereas 16 new spots have been registered and four sites have been eradicated. Seeds produced by mature lianas revealed to be viable and able to germinate in the wild. Kudzu has thus passed the naturalization stage and may soon enter the phase of a possible rapid expansion, what suggests adopting a strategy of systematic eradication of the species in the mid-term. Preliminary tests allowed to confirm the efficiency of the chemical and the mechanical (surgical removing of root crowns) control methods, the last allowing the treatment of kudzu in forest and in protected areas as well. Kudzu represents thus a good example for how combining early detection, better understanding of the ecology, and the development of suitable eradication methods of the species may allow to control or even systematically eradicate a species at reasonable costs.